Gimbals
A gimbal is a ring that is suspended so it can rotate about an axis. Gimbals are typically nested one within another to accommodate rotation about multiple axes.
They appear in gyroscopes and in inertial measurement units to allow the inner gimbal's orientation to remain fixed while the outer gimbal suspension assumes any orientation. In compasses, flywheel energy storage mechanisms, or more commonly drink holders, they allow objects to remain upright. They are used to orient thrusters on rockets.
Some coordinate systems in mathematics behave as if there were real gimbals used to measure the angles, notably Euler angles.
For cases of three or fewer nested gimbals, gimbal lock inevitably occurs at some point in the system, due to properties of covering spaces (described below).
Read more about this topic: Gimbal Lock