Google AdSense will use mainly 3 ways to target users: by context, by location and by personal information. With the benefits and value that advertising can bring to a brand, an advertiser, it is essential that advertising content is delivered to the right users. This is something you can use to get both users and advertisers more interested in your site.
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In Content Ads - Best Practice
These 3 sizes are very popular in programmatic due to high demand by advertisers and because they yield higher CPM.