Core rule
Actions
An action is a resource used for attacks, spells, and other abilities. You normally have one per turn.
An ability that costs an action spends it when used. Your bonus action and movement may still be available.
Features such as Extra Attack and effects such as Haste change what you can do. The number of attacks is not always the number of actions.
Action1Bonus action1Reaction1
Movement is separate. Reactions may be used on another creature’s turn and refresh at the start of yours.