Final answer:
In Scratch, a broadcast block is used to communicate when the menu should appear, allowing for interaction between different sprites.
Step-by-step explanation:
In Scratch, when adding a menu to your game, the type of block used to communicate when the menu should appear is called a broadcast block. This block can send a message to other sprites, triggering scripts that contain the 'when I receive [message]' hat block.
For example, you might have a broadcast block that sends a message 'show menu', and in your menu sprite, you would have a script starting with 'when I receive show menu' that then contains the blocks that display the menu elements on the screen.