Google uses a comibnation of three primary factors to determine when an ad ahsows on the result page.
- Bid
The Bid is the price you are willing to pay for a chlick on your ad. - Quality and relevance of the ad
Your ad need to be relevant to the search being made in order to show on the search result page - Landing page experience
When someone clicks on yor ad, the landing page that they are sent to should have similar content as the ad itself