Imagine your Scratch cat is sitting on the screen, doing nothing. It's waiting. How does it know when to start moving, or meowing, or dancing? It waits for something to happen — and the thing that happens is called an event.
An event is just something you do: clicking the green flag, tapping the cat, or pressing a key on the keyboard. Every event says, in a way, "when this happens…" — and then Scratch runs the blocks you stacked underneath. That's the big idea:
when something happens → then do these blocks.
You already play this game every day! When the doorbell rings, then you go to the door. When your name is called, then you look up. Programs listen for their events in exactly the same way.
In Scratch, an event block has a curved top, like a little hat — so we call it a hat block. It's the block that goes on top of a stack. Nothing can clip on above a hat, because it's always the first thing. Then all the "do this" blocks snap on underneath, one after another.
Here is a hat block sitting on top of a stack. The blue hat is the event — "when the green flag is clicked" — and the blocks below are the ones that will run when it happens.
The whole thing together is called a script: one hat, plus the blocks below it. When the event happens, Scratch runs the script from the top downwards, just like reading a list.
Scratch has lots of events, but these three are your best friends when you're starting out:
Because each event has its own hat, you can build a little game in no time. One script says "when the green flag is clicked → go to the middle". Another says "when the space key is pressed → jump up and come down". Now you have a game where pressing space makes your sprite hop!
Then the cat probably has no "when this sprite is clicked" hat with blocks under it! An event only does something if you've stacked blocks beneath its hat. A lonely hat with nothing underneath is like a doorbell with no one home — it rings, but nothing else happens. Snap a "meow" block under the hat and try again.
Yes — and that's the fun part! A sprite can have a "when green flag clicked" script and a "when space key pressed" script and a "when this sprite is clicked" script, all at once. Each hat listens for its own event and runs its own stack of blocks. Different events, different scripts, all waiting patiently for their turn.
Here's the clever bit. A program with event blocks doesn't rush ahead — it waits. It sits quietly, listening, until an event happens. Then it reacts: the blocks under the matching hat run. When they finish, it goes back to waiting for the next event. This is how programs feel alive and answer to you.
Think of a script like a set of instructions with a rule on the front:
Those three "jump" blocks are patient. They do nothing at all until you press space. Press it, and they run top to bottom — up, wait, down — and the sprite hops. Let go and press again, and they run again. The event is the trigger; the blocks are what it triggers.
The blocks under an event hat only run when that event happens — not straight away when the program starts! It's easy to think "I put a meow block in, so the cat should meow." But if that block is under a "when this sprite is clicked" hat, the cat stays silent until you actually click it. And a hat with nothing stacked underneath does nothing at all — the event happens, but there are no blocks to run. Remember: different events start different scripts, and each one waits for its own moment.