This action block allows you to send card views with a carousel view inside the conversation area. You can add up to 10 different cards. Each card can contain a title, subtitle, Image and up to 3 buttons. These buttons can be Show URL, Postback, Call Number, Share type buttons.
You can check FB Messenger documentation for Generic template from this link https://developers.facebook.com/docs/messenger-platform/send-api-reference/generic-template