The Ring on a Ribbon gives him something to look up at. He can reach for it and will eventually pull it into his mouth. It also gives him an incentive to move.
He isn't very mobile he just kicks a lot and slowly pulls himself forward with his arms. He can move a couple of inches and that's a start.
He is strengthening the muscles in his arms, legs, back and neck and gaining coordination as he reaches for that ring. He will need to push himself up further before he will be able to grasp it.
This is one way we are adapting his environment to his developing needs. Not just a physical need either. Providing him with a new challenge also gives him mental stimulation, something to think about and work towards. When he gets there the rewards will be great.