You use back to talk about returning to a point where someone or something has been before. If you go back, you return to the place you left; often this place is mentioned.

1. I had lent my apartment to a friend for the weekend and when I got back I found that the reading lamp would not work.
2. Days later, I came back to the spot.
3. No, I’m not going back inside.

If someone moves backwards, they move in the opposite direction to the one that they are facing.

4. He was jerked off his feet and dragged backwards.
5. The hummingbird can hover and even fly backwards.

You use either back or backwards to talk about moving to a position behind you without turning round.

6. Then they stepped back, laughing with triumphant pleasure.
7. ‘And the Russians, of course,’ he said, rocking back comfortably on his stool.
8. She stepped backwards onto a coffee cup.
9. Stuart moved backwards into a corner.