Two meanings of the same acronym
In the US, "SEM manager" or "SEM agency" almost always refers to paid search: building Google Ads and Microsoft Advertising campaigns, managing bids and writing ads. In Europe, and in many textbooks, SEM is the sum of SEO and paid search. Neither use is wrong, but mixing them up leads to contracts that do not cover what you expected.
Whatever the label, the logic is the same: on a results page, searchers see both ads and organic listings, and showing up in both increases the share of clicks you capture for a query.
Why paid and organic search belong in one plan
Each channel produces data the other cannot generate on its own:
- The Google Ads search terms report shows the exact queries that produce sales, which are the best topics for new SEO pages.
- Search Console reveals queries where you get impressions but rank on page two; ads can cover that gap while content improves.
- Ad headline tests show which selling points earn clicks, ready to reuse in title tags.
- On branded searches, test whether ads bring incremental clicks or simply replace free organic ones.
Splitting the budget
There is no universal ratio. A new site with no organic traffic relies almost entirely on paid search to get leads quickly. A site already ranking for its core terms keeps ads for highly competitive keywords, seasonal offers and service areas where it is not visible yet.
To decide, compare the cost of an SEO page (writing, development, links) with the value of the clicks it can replace: expected monthly clicks × the keyword's CPC. Then track a blended cost per acquisition across paid and organic instead of two dashboards that never talk to each other.