Nearly everything physical in the world can be interacted with. Doors, chests, levers, walls, floors, chandeliers, vehicles, mounts, terrain features, traps, and magic objects are all part of the environment. The setting is not just decoration—it is a toolbox.
Good players treat the environment as part of the encounter. A crumbling bridge, loose rocks, or a hanging lantern can be used creatively to gain advantages or avoid danger entirely.
You can break, climb, unlock, move, push, pull, ride, jump, or manipulate objects. The DM determines which ability or skill applies, often based on how you describe your action. Creative solutions are rewarded, even if no exact rule exists.