Skippable In-Stream ads appear before, during, or after videos, as well as in full-screen placements within the mobile app. Viewers can skip the ad after 5 seconds. Under the CPV bidding model, you are charged when a user watches 30 seconds of the ad (or the full video if it is shorter) or interacts with the ad. When using Target CPM, Target CPA, or Maximize Conversions strategies, charges are applied based on impressions rather than views.
Source: Google support
Non-Skippable In-Stream ads run up to 60 seconds and can appear before, during, or after a video. Viewers cannot skip these ads, and you are charged for every impression.
In-Feed Video ads feature a thumbnail and accompanying text. Their format and size adapt to the placement. Charges apply only when a user clicks to watch the video or, in certain cases, when the video auto-plays for at least 10 seconds.
Source: Google support
Bumper ads are non-skippable and have a maximum length of 6 seconds. They can appear before, during, or after a video, and you are charged for every impression.
YouTube Shorts ads are displayed in the same way as standard, organic Shorts. Costs are incurred based on impressions, TrueView ad views, or user interactions.
Source: Google support