When you tap Play, script blocks *execute* and do their thing. E.g. [[Set Score]] sets the current score, so if we wire the [[Number]] 3 to it, the score is set to 3.

Blocks execute top-to-bottom, left-to-right. But you can plug in the yellow *control wires* to change the execution order. This is especially useful when you want to execute a block only some of the time. E.g. here I've wired a [[Button|Can't find buttons, motors, characters?]] to [[If]] to [[Win]], so when the player moves onto the button, then the game is won: