How SEM works
Advertisers bid on keywords related to their products or services. When someone searches for one of those terms, an auction decides which ads appear, and the advertiser pays when an ad is clicked (pay-per-click).
SEM vs SEO
- SEM (paid search): immediate visibility and full control over budget and targeting, but the traffic stops when you stop paying.
- SEO: unpaid rankings that take longer to build but keep bringing visitors without a cost per click.
Used together, paid search covers keywords you don’t rank for yet, while SEO lowers your reliance on ads over time. Search term data from ads also shows which keywords convert, which helps plan SEO content.
Key SEM metrics
Impressions, click-through rate (CTR), cost per click (CPC), conversion rate, cost per acquisition (CPA) and return on ad spend (ROAS).
SEM, SEO and PPC: how the terms relate
| Term | Usually means |
|---|---|
| SEO | Earning unpaid results. See SEO |
| PPC | Paying per click on ads. See pay-per-click |
| SEM | The umbrella for search marketing, most often paid search, sometimes SEO and paid together |
A simple SEM structure
A paid search account is organized into campaigns (a goal or product line), ad groups (a theme of keywords) and ads. Keep each ad group tight, so the ad matches the search and the landing page.
SEM steps
- Set goals and conversion tracking.
- Research keywords and group them by intent.
- Write ads and build landing pages.
- Set budgets and bids, and launch a small test.
- Review search terms, add negatives, test ads and improve.
- Use what the data shows to guide SEO as well.
SEM FAQs
Is SEM the same as PPC?
Often, yes. Some people use SEM to mean paid search only, others to mean paid and organic together.
Which is better, SEM or SEO?
Neither alone. Use paid search for speed and control, and SEO for lasting traffic. See our Google Ads service and SEO service.