Pay-per-click (PPC) is primarily based on keywords. Advertisers bid on specific keywords or phrases that users might search for when looking for specific products or services. When a user searches for these keywords, ads are displayed at the top of the search results using a bidding system. In case a user clicks on an ad, the advertiser has to pay a fee to the publisher or the advertising platform. The goal here is to choose keywords that get more clicks, driving leads for businesses.