What is a gyroscope?

A gyroscope is a set of spinning wheels or disks that tend to stay stable in space. The simplest examples are spinning tops or bicycle wheels. Once moving on a bicycle, it is easier to remain upright because the wheels are acting like gyroscopes and are stable in space. Torpedoes use gyrocompasses for the same reason. No matter which way the weapon turned, the gyroscope tended to stay stationary in space, pointing to the same direction.