Fabric filled with foam, feathers, or other padding material makes a cushion, which can be used to make something like a chair or sofa more comfortable.
The noun cushion can also refer to anything that is used to soften an impact or absorb shocks. In modern cars, for example, sometimes in a crash or accident, air bags will deploy and act as cushions for the passengers to prevent them from injuring themselves on hard surfaces like the dashboard or steering wheel. A cushion isn't necessarily a physical one, however, as you may want to keep an emergency fund as a cushion in case of unexpected expenses. As a verb, cushion means to protect from the impact of negative information so if you have bad news, you'll want to cushion the blow as much as possible.