A client who wants to advertise before, during, or after popular videos on the Display Network should:
- create a video ad campaign
- add a call-to-action (CTA) overlay to video ads
- add the keyword “video” to relevant campaigns
- bundle display ads for each target audience
Your video ad plays before, during, or after other videos. After 5 seconds, the viewer has an option to skip the ad. Viewers see videos they’re curious about, and you get more views from an audience you know is interested. Because you choose what you want to pay for a view, you get the right audience at the right price. Unlike cost-per-impression (CPM) pricing, you won’t need to pay every time your ad is shown.
TrueView video ads under video campaigns give viewers control over which advertisers’ messages they want to see and when. Use this format when you want your video ad to appear before, during, or after other videos on YouTube and the Display Network.
Read more here: https://support.google.com/partners/answer/6052202