The literal definition
SEO = Search Engine Optimization. In some job listings you will also see it expanded as 'search engine optimisation' (British spelling) or shortened to 'organic search'. All three refer to the same thing: earning unpaid placement in search results, as opposed to buying it through ads.
What the work actually consists of
Three buckets. Technical SEO makes pages crawlable, indexable and fast. On-page SEO makes each page's content, headings, titles and structured data match what a searcher wants. Off-page SEO builds the citations, links and brand signals that make a site credible enough to be recommended.
Why 'SEO' now includes AI answers
Search no longer ends at ten blue links. Google AI Overviews, ChatGPT search, Perplexity and Copilot all answer directly and cite a handful of sources. Optimizing to be one of those cited sources is called AEO (answer engine optimization) or GEO (generative engine optimization) - a modern extension of SEO, not a replacement for it.
What SEO is not
It is not keyword stuffing, buying links, or spinning articles. Those tactics are explicitly against Google's spam policies and now trigger algorithmic suppression rather than slow decay. It is also not a one-time project: rankings move because competitors publish, algorithms update, and content ages.
How you know it is working
Impressions and clicks in Google Search Console, average position for your target queries, the number of pages indexed, and - increasingly - how often your brand is cited in AI answers. Traffic alone is a lagging indicator; indexation and impressions move first.