SEM (Search Engine Marketing)

SEM has two meanings in active use. The narrow and dominant one in 2026: search engine marketing = paid search advertising on Google Ads, Microsoft Ads, and the search networks they power. The broader, older meaning: all marketing through search engines, including organic SEO and paid. Most practitioners use the narrow meaning; older textbooks use the broad one.

SEM and AEO/GEO interact in two non-obvious ways. (1) AI search is eroding paid-search inventory. When Google AI Overviews answer a query directly, the user often doesn't scroll to the ads beneath. Cost-per-click is creeping up on the queries that still send commercial traffic; volume on those queries is shrinking. (2) AI engines themselves are starting to introduce ads. ChatGPT Search has begun limited sponsored placements, Perplexity has experimented with sponsored questions. The shape of paid placement in AI search is unsettled; methodology may diverge meaningfully from Google Ads.

For a marketing programme in 2026, SEM still has measurable ROI for high-intent commercial queries but the long-cycle visibility budget is shifting toward GEO and AEO. The mix question (what fraction of search budget should be paid vs organic vs AI-search) has no canonical answer yet; programmes are running quarterly experiments.