There are the more usual display ads on YouTube, and then there are ones that look like this:
What does YouTube call these ads?
How can one activate them?
To activate display ads on youtube.com you should create a display campaign, then you should go to +Targeting and add youtube.com as a placement.
Your ad will run on youtube.com depending on the language and country settings of your campaign. For example if you want your ad to be seen only by youtube viewers from USA you should add USA from Locations (campaign settings).
They are called Call-to-Action overlays. Check this help page for more info.