There are occasions on which it is not a simple task to know if a body is at rest or moving.
When we are riding a bicycle we can clearly see that we are moving with respect to the road.
If we are sitting in a car our sensation of movement is not so clear.
If we are in a train, a really large vehicle, we have the illusion that it is the scenery which is moving and not us.
Our planet is enormous compared to a train, which is why although all the earth moves, it seems to us to be still, and the sky around it the one that moves.