A click on a companion banner:
- All of the listed answers are correct
- counts as a view even if the person hasn’t watched 30 seconds of the ad
- can direct to a YouTube channel
- can direct to an external URL
Explanations:
Companion banner is a clickable thumbnail image that accompanies a TrueView in-stream ad. On a YouTube page, it appears next to the ad, in the top right corner (on a desktop computer). A click on a companion banner: can direct to an external URL or a YouTube channel and counts as a view, even if the viewer hasn’t watched 30 seconds of the ad
Companion banners are optional. They’re also displayed only in certain cases, for example, in the context of a YouTube watch page. They don’t show on embedded players, connected TVs, or game consoles.
A click on a companion banner:
- can direct to an external URL or a YouTube channel
- counts as a view, even if the viewer hasn’t watched 30 seconds of the ad
Read more here: https://support.google.com/partners/answer/6293542?hl=en