Ads are likely to be most contextually relevant to the sites on which they appear when using:
Remarketing
In-market audiences
Affinity audiences
Topic targeting
Explanation:
Contextual targeting: This type of targeting is used to match your ads to sites or pages (also known as automatic placements) based on the keywords or topics you’ve chosen.
You can read more here: https://support.google.com/adwords/answer/1704368?hl=en