Search Engine Marketing (SEM) is the broader discipline that, unlike SEO, includes paid search advertising in addition to organic results. The paid side centers on PPC (pay-per-click) advertising, exemplified by Google Ads, Google's platform for running search, display, video, and other types of ads. Search ads are text ads that appear on SERPs when users search specific keywords, while display ads are visual banner or image ads shown on websites, apps, or videos across a display network. A campaign objective in platforms like Facebook Ads—the primary goal chosen for a campaign—guides optimization toward conversions, traffic, reach, or other outcomes. Google Shopping (Product Listing Ads) shows product images, prices, and merchant names in shopping results, fed by a structured product feed listing product data like titles, prices, and images.
Paid search campaigns target keywords through configurable match types: broad match, phrase match, exact match, and negative match. Negative keywords explicitly exclude irrelevant searches so ads don't appear for them. Ad Rank, the value determining ad position, is calculated from bid amount, Quality Score (a rating of keyword and ad relevance and landing page experience), and other factors, with more relevant ads often earning lower cost per click. Pricing models span CPC (cost per click—the amount paid each time someone clicks the ad), CPM (cost per mille, the cost per 1,000 impressions), and YouTube formats like YouTube pre-roll ads that play before main content, skippable in-stream ads that viewers can skip after a few seconds, non-skippable in-stream ads that viewers must watch in full, and TrueView campaigns that typically charge only when viewers watch or interact. Click-through rate, \(\text{CTR} = \frac{\text{Clicks}}{\text{Impressions}} \times 100\), measures ad engagement, and the total amount of time viewers spend watching is captured as watch time.
Performance metrics frame every paid campaign. Return on ad spend (ROAS) measures revenue generated per dollar of ad cost and is calculated as \(\text{ROAS} = \frac{\text{Revenue from Ads}}{\text{Cost of Ads}}\). The break-even ROAS is the level at which revenue exactly covers ad cost with zero profit, found using margin and pricing. Bidding strategies control how the ad platform sets bids; automated options include Maximize Conversions, Target CPA, and Target ROAS. Frequency capping limits how many times an individual user sees an ad in a given period, helping control exposure without overwhelming users. Finally, the landing page in SEM is the specific page users reach after clicking—the place designed to match search intent and drive conversions, covered in more depth in the next chapter on CRO.