Hi Sarah! Hit and beat can mean different things depending on the context.
Both words can mean to physically hurt someone. But to hit someone usually means to hit him only once. To beat someone, on the other hand, usually means to hit someone multiple times.
"Hit" can also mean to reach a certain target.
"Beat", on the other hand, can also mean to defeat someone.
Another definition--- In the expression "Beat it", you say this when you want something or someone to go away.