SEM vs SEO: is search engine optimization part of SEM?

Whether SEM includes search engine optimization depends on who's using the word. Some marketers use SEM, search engine marketing, as the umbrella for everything that brings traffic from search engines, paid and unpaid, which puts SEO inside it. Others use SEM for paid search alone: ads bought through Google Ads or Microsoft Advertising, with SEO as its unpaid counterpart.

Neither use is wrong, but they produce very different proposals and budgets. When an agency offers "SEO and SEM services", the first question is which meaning it has in mind.

What doesn't change is the mechanics. SEO earns positions in the organic results, which Google says it doesn't sell. Paid search buys positions in the ad slots, which Google sells by auction. Both appear on the same results page, which is why the terms get blurred.

The two meanings of SEM

If a document uses "SEM" and "SEO" side by side as two line items, it most likely means the paid-search sense. If it says SEM "includes" SEO, it's the umbrella. When in doubt, ask whether the SEM figure includes ad spend.

SEM, SEO, PPC and the terms people mix up

So "SEO PPC SEM" on a proposal usually means organic work, ad management, and the umbrella over both. For how paid search works on its own, see SEM, explained; for the unpaid side, see what organic search is.

Where SEM and SEO share the work

• Keyword research. One list of searches drives both ad keywords and page topics. Google Ads' search terms report shows the real searches that led to your ads being shown and clicked, which is a ready-made list of phrases to consider for pages.
• Landing pages. In Google Ads, the quality of your ads and landing page is one of the inputs to Ad Rank. In organic search, the same page has to be the most useful answer to win. A fast, clear, relevant page serves both.
• Search Console. Linked to Google Ads, it powers the paid and organic report, which shows how often your ads and your organic listings appear for each search, separately and combined.
• Analytics. GA4 reports Paid Search and Organic Search as separate default channels, so you can compare them on enquiries and sales rather than clicks.

Where SEM and SEO don't overlap

• How position is decided. Ads are ordered by Ad Rank, an auction score worked out on each search from your bid, ad and landing-page quality, the search context and a few other factors; how PPC auctions and Quality Score work has the full list. Organic results are ordered by Google's ranking systems, with no auction at all.
• Money. Ad spend and organic rankings are kept apart: Google states that payment can't buy more frequent crawling or a higher organic position.
• Timing. Ads can show as soon as a campaign is live and stop when the budget does. Organic changes are slower and less predictable: Google's guidance is that they can take anything from hours to months to have an effect.
• Labels. Google groups text ads under a "Sponsored results" label that stays visible as people scroll, and lets searchers collapse them with one click. Organic results carry no label.

SEM and SEO in AI search

Google's AI features have both sides too. On the paid side, Google Ads now places ads above, below and inside AI Overviews and in AI Mode, drawing on existing Search, Shopping and Performance Max campaigns, with no separate targeting or opt-out. On the organic side, the entry ticket is the same as for normal results: an indexed page that's allowed a snippet, with no special optimization on top.

Outside Google, assistants such as ChatGPT and Perplexity cite pages they can fetch and read. That's organic work: crawler access, content in the HTML and pages worth citing. SEO vs AEO vs GEO explains how the newer labels relate to SEO.

What SEO and SEM services include

"SEO and SEM services" are usually two services sold together, with different skills, rhythms and costs. Before you compare SEO SEM companies, line the proposals up against these questions:

For deciding how to split money between the two, SEO vs SEM: when to use each walks through the trade-offs. We don't run ad campaigns. If you want the organic half handled, our done-for-you service audits your key pages and makes the on-page fixes.