YouTube announced a new interactive video feature to ask for a call to action (CTA), to give viewers an option to view related videos and to poll your audience to learn what they think. The new feature is called “Cards.”
According to YouTube:
You can use cards to add interactivity to your videos. Cards can point viewers to a specific URL (from a list of eligible sites) and show customized images, titles, and calls to action, depending on the card type.
Poll cards let you take an instant survey of your audience. You can insert up to five multiple-choice questions, to poll the audience.
Here is more information about YouTube Cards https://support.google.com/youtube/answer/6140493?hl=en