A variable means to store information in a smaller reference. You can use variables to store , numbers and the like in Scratch too.
First do all the usual stuff like green flag and sprites,
Go to the Data section and click ‘Make a Variable’ and call it ‘score’ then hit enter.
Now add the ‘change [score] by ’ block to your script. Click the green flag and the ‘score’ variable in the top-left corner will add one.
This seems simple but is actually quite useful!
Extra challenge: You can use this to add scores in a game when something is pressed or touched.