On the Google Display Network, your ad is eligible to show on a webpage if your:
- Landing page matches that webpage’s content
- Website matches that webpage’s content
- Keywords match that webpage’s content
- Ad text matches that webpage’s content
Keywords match that webpage’s content
Google algorithm analyze the content of WebPages where you ad going show. The Google will show your ads to those pages where content and keywords are relevant to your ad (your business niche) to give you best possible conversion. Your ad placement depends on factors like keywords and topic selections, your language and location targeting, a visitor’s recent browsing history, and others.
Read More Here:- https://support.google.com/google-ads/answer/1726458?hl=en