Now consider a swing. A boy swings forward and back on it.

The swing is moving. So the swing has mechanical energy.

Is the swing moving? Yes. The swing has mechanical energy.

Now the swing hangs still. Nobody is on it.

The swing is not moving. So the swing has no mechanical energy.

Is the swing moving? No. The still swing has no mechanical energy.

Now consider a top. The top turns round and round on the floor.

The top is moving. So the top has mechanical energy.

Now consider a bird flying across the sky.

The bird is moving. So the bird has mechanical energy.

The top turns, and the bird flies: both have mechanical energy. The parked bike sits still: no mechanical energy.