PPC (Pay-Per-Click) Advertising: PPC is a model where advertisers pay a fee each time their ad is clicked. It’s commonly associated with search engine advertising platforms like Google Ads (formerly known as Google AdWords) and Bing Ads, as well as social media platforms like Facebook Ads and LinkedIn Ads.

PPI (Pay-Per-Impression) Advertising: PPI, also known as CPM (Cost Per Mille), is a model where advertisers pay a fee based on the number of times their ad is displayed (impressions), regardless of whether the ad is clicked or not.