The Overlay by IAB is a standard ad unit that is displayed as a pop-up window on the page viewed by the user.
Video ads appear in the video as a semi-transparent banner. Usually at the bottom of the screen. Advertising banners appear during the video broadcast, showing streaming ad units to the viewer. The viewer has the opportunity to click on the ad space to open a larger advertising screen or go to the advertiser's site.
The Overlay can increase brand awareness, to promote some product or service, and increase daily traffic to the company's website. One of the useful features of this advertising model is the use of advertisers contextual comparison with content. This increases the viewer value, interest and potential participation. The overlay is one of the most effective ads, so they should always be included where it is possible.