Not wind up, that would use a spring.

A spinning top is an example of a flywheel.
My son had a flywheel based car that you put in a base and turned a crank, spinning the wheels faster, faster and faster. The flywheel inside would make quite a noise as it spins to store the energy from the crank. Then you'd let it go and it zoomed across the floor.

Commercial flywheels are sealed in a vacume of special gas to reduce friction, made of a composite material and as mentioned uses special zero friction magnetic bearings. These flywheels used for energy storage range in size from about a foot square to much, much taller ones.

Probably the most widely used flywheel storage sytem is for computer power back-up system. Typically it would provide enough time for a proper shut down of many computers connected in a network.

The idea is to use an electric motor to gradually spin a heavy flywheel up to speed, then maintain that speed. Imagine 50lbs or so spinning at several hundred thousand RPM's.
When the power goes out the motor converts to a generator (Like our cars electric motors do) and runs the backup system for computers, etc.

If you do a google search on flywheels the reading can be fascinating.

Efficient drivers do it better.
1003 miles a tank personal record. 74MPG calculated. HCH1 CVT