SEO explained from scratch — how search engines decide what to rank, what actually moves the needle, and why SEO in 2026 means optimising for both Google and AI.
SEO — Search Engine Optimisation — is the practice of improving a website so it appears higher in search results and attracts more organic (unpaid) traffic. That's the textbook definition. But in 2026, it's incomplete.
Search is no longer just Google. It's ChatGPT, Perplexity, Google AI Overviews, and Gemini. People search by asking questions and expect direct answers — not ten blue links. SEO still matters enormously, but the landscape it operates in has fundamentally changed.
This guide explains how SEO works, what the three pillars are, how Google actually decides what to rank, and what effective SEO strategy looks like now.
Before you can optimise for search engines, you need to understand what they do. Every major search engine — Google, Bing, DuckDuckGo — operates a three-stage process:
Search engines send automated bots (called crawlers or spiders) across the web. These bots follow links from page to page, discovering new content. If a page has no links pointing to it, crawlers may never find it — and if they can't find it, they can't rank it.
Crawlers follow rules. A file called robots.txt on your website tells crawlers which pages to access and which to skip. Getting this wrong — accidentally blocking important pages — is one of the most common technical SEO mistakes.
Once a crawler reads a page, it processes the content and stores it in an index — a massive database of everything the search engine has read. When someone searches, Google doesn't scan the web live. It queries its index.
Not everything crawled gets indexed. Google applies quality filters — thin content, duplicate pages, and content flagged as low-value may be excluded. Getting into the index is step one. Getting ranked well is step two.
When someone enters a query, Google's algorithm determines which indexed pages are most relevant and authoritative — and in what order to show them. The algorithm evaluates hundreds of signals simultaneously. The most important ones fall into three categories: relevance, authority, and experience.
SEO work divides into three interconnected areas. Ignoring any one of them creates a ceiling on what the other two can achieve.
Technical SEO ensures search engines can crawl, index, and render your site correctly. It has nothing to do with content — it's about infrastructure.
Technical SEO doesn't directly improve rankings on its own — but it removes the ceiling. You can have the best content in the world and rank nowhere if Google can't crawl and index it properly.
On-page SEO is the process of optimising individual pages to rank for specific queries. It covers everything visible on the page — headings, copy, images, internal links — as well as the invisible elements like title tags and meta descriptions.
The goal is to make each page a clear, direct, authoritative answer to the query it targets. We cover on-page SEO in depth in our complete on-page SEO guide.
Off-page SEO is about building your site's authority through external signals — primarily backlinks. A backlink is a link from another website to yours. Google interprets links as votes of trust: if authoritative sites link to you, you're probably trustworthy too.
Not all links are equal. A single editorial link from a high-authority publication outweighs hundreds of low-quality directory links. Quality, relevance, and context all matter. Read our full guide to backlinks for the mechanics and strategy.
Google has never published its full ranking algorithm — and it changes hundreds of times per year. But from a decade of analysis, leaked documents, and empirical testing, the core factors are well understood.
The single most important ranking factor is whether your page matches the searcher's intent. Google classifies every query by intent — informational ("what is"), navigational ("company name"), commercial ("best X"), transactional ("buy X"). A page that doesn't match intent won't rank regardless of how well optimised it is.
Google's Helpful Content system rewards pages that are genuinely useful to the person reading them — not pages written primarily to game rankings. Depth, accuracy, originality, and demonstration of real expertise (E-E-A-T) are all evaluated.
Authority flows through links. A page with many high-quality links pointing to it has more authority and ranks higher — all else being equal. Domain-level authority matters too: new domains take longer to rank because they have no established trust signal history.
Google uses Core Web Vitals and behavioral signals (though it denies the latter publicly) to assess whether users are satisfied with a page. A page that loads fast, is easy to use, and keeps visitors engaged is treated more favorably than one that's slow and bouncy.
Experience — Has the author actually done the thing they're writing about?
Expertise — Do they have relevant knowledge or credentials?
Authoritativeness — Is the site/author recognised as authoritative in their field?
Trustworthiness — Is the content accurate, transparent, and honest?
This is the most common question in SEO — and the honest answer is: it depends, and anyone who gives you a specific number without knowing your site is guessing.
As a general framework:
SEO compounds over time. A page that ranks #5 today can move to #1 in 6 months as it accumulates links and engagement. This is the fundamental difference from paid advertising: SEO builds an asset that appreciates. Ads disappear the moment you stop paying.
The biggest shift in search since mobile happened between 2023 and 2026: AI-generated answers became the dominant format for high-intent queries.
Google AI Overviews appear at the top of results for nearly half of all searches. ChatGPT handles over 100 million queries per day. Perplexity crossed 100 million monthly users.
The signals that drive AI citations overlap significantly with traditional SEO — authoritative content, clean technical infrastructure, strong external links — but the output is different. In AI search, the goal isn't to rank #1 in a list. It's to be named within a generated answer.
Effective search strategy in 2026 optimises for both simultaneously. Good SEO practice feeds AI visibility. AI-optimised content tends to perform better in traditional search. They aren't competing strategies — they're two faces of the same discipline.
For a deeper look at how the two interact, see our guide on GEO vs SEO and the Locully AI Search Visibility service.
Yes — categorically. Organic search remains the largest source of website traffic globally. The channels have expanded (AI search, voice search), but Google still processes 8.5 billion searches per day. The question isn't whether to do SEO. It's whether your SEO strategy also accounts for AI search.
SEM (Search Engine Marketing) covers both paid and organic search. SEO is specifically the organic component — improving rankings without paying for ad placement. Google Ads (PPC) is paid search. Many organisations run both in parallel: ads for immediate traffic, SEO for long-term organic growth.
Partially. Content optimisation, internal linking, and basic technical checks (fixing broken links, writing title tags) can be managed by a capable non-specialist. Technical SEO audits, schema implementation, and authority building campaigns typically require specialist knowledge or tools. The return on hiring a specialist for those areas tends to outweigh the cost.
Google's spam detection has become significantly more sophisticated since the introduction of machine learning-based ranking systems. Tactics that worked in 2015 — keyword stuffing, low-quality link schemes, thin content — are actively penalised today. The safest and most durable approach is also the correct one: produce genuinely useful content, earn real links, and build authority through expertise.
For small to medium businesses in competitive markets, effective SEO typically requires ฿20,000–80,000/month in agency or specialist costs, depending on content volume, link building, and technical scope. One-off packages for specific deliverables — content sprints or backlink campaigns — are available at lower entry points. See our packages page for fixed-price options.
The complete on-page SEO playbook — every element that affects how Google ranks individual pages, from title tags to content structure to E-E-A-T signals.
Read articleHow Google uses backlinks to measure authority, what separates a valuable link from a worthless one, and the link building strategies that still work in 2026.
Read articleProgrammatic SEO explained — how to build hundreds of search-optimised pages from data at scale, the 12 proven playbooks, and the quality line between ranking and penalty.
Read articleWe'll run your brand across ChatGPT, Perplexity, and Google AI Overviews — and show you exactly what it would take to get recommended.
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