To understand the Broadcast and Recieve event blocks, lets think of it in another way. The
Broadcast Eventis like the phone that sends the text message, or someone throwing a ball. TheWhen i Receive event --is like the phone that gets the text message, or the person that catches the ball.
The Key on both of them is what links the two together. Think of it as the text message between the phones, or the ball that they are throwing. You can call it whatever you'd like, as long as its the exact same

Lets do an Example of how to use it
On one block which we'll use as the button, put a
when touched by a playerblock followed by ourBroadcast event --.
On another block, place the
When i Receive event --and put what you want to happen when someone presses the button. In this case we want to change the players scale so we use achange all players scale to 1.