This is a popular message type in Facebook Messenger, providing the user with a scrollable horizontal gallery of images with titles, descriptions, and buttons. Some chatbot designers use the term “carousel” instead of “gallery”.
You can have up to 10 cards in each gallery with up to 3 buttons in each. Galleries are often used for complex bot menus and displaying lists of similar items (e-commerce products, restaurant menus, etc).
GALLERY block editor
You can upload images or use URLs exactly the same way as in the IMAGE block, the only difference is that you can add card titles and descriptions. Gallery cards are expanded in the visual builder so that you are able to connect each button to different blocks.
Activechat has an awesome feature of dynamic galleries. These galleries can be generated on-the-fly and can be used for product listings and shopping carts in e-commerce. Dynamic galleries are described in more detail in: