If something skyrocketed, it means it went up very fast, like a rocket going into the sky.
When something skyrocketed, it usually means it went up a lot and very quickly. It's often a good thing, like when prices go up or when a team's score goes up a lot.
Examples:
The price of the house skyrocketed.
Her grades skyrocketed after she started studying more.
The number of people at the party skyrocketed.
The number of cookies I ate skyrocketed after I saw how good they were.
The demand for the new toy skyrocketed, and everyone wanted one.
The number of stars in the sky skyrocketed when the aliens came to visit.