Originally, the space shuttle was meant to be a transport system to and from a space station.
Due to financial cutbacks and shifts in priority at NASA, the space station never materialized back then, but the space shuttle did.
The space shuttle became an orbiting laboratory as well a reusable spacecraft for transportation into space.
A major key to its success is its flexibility in taking on different kinds of missions, while being reusable.
It can perform maintenance and repairs on satellites as well as scientific research.
The shuttle can carry up to eight astronauts, or ten if necessary. It is designed to stay in orbit for up to 10 days, though 5 days is the typical length of a mission.
While the space shuttle has had its disasters, it seems to be remarkably successful.