[Gareth321]

The ads which the "ad free" Premium service permits:

1. Sponsored in-video ads.

2. Ad overlays on videos (at the discretion of content creators).

3. Merchandise store ads below videos (also at the discretion of content creators).

4. YouTube and Google ads for various products and services in the video feed.

[voxic11]

Ah I also use uBlock Origin so I guess that is why I haven't seen #4.