An advertiser is preparing a Google Display campaign and needs to distinguish between creative elements. What's the difference between assets and ad types in this context?

Assets are the creative elements provided by the advertiser, while ad types are the format for presenting them. Assets are the building blocks: headlines, descriptions, images, logos and videos. Ad types are the formats those blocks are assembled into and shown in, such as responsive display ads or uploaded display ads. The distinction matters in practice because it explains how responsive formats work. The advertiser supplies a set of assets, and the system combines them into ads sized and shaped for each placement across the Display Network, testing combinations and favouring those that perform. That is why asset variety and quality are the advertiser's real lever: more strong headlines, images and logos give the system more to work with, whereas a thin asset set limits how many placements the campaign can compete for.