What is meant by wormhole?

Could you please elaborate on the concept of "wormhole" for me? I've heard it mentioned in relation to theoretical physics and cosmology, but I'm not quite sure what it signifies. Is it a type of bridge or tunnel in space? Does it have any practical applications in the realm of astrophysics or quantum mechanics? Additionally, are there any theoretical models or experiments that have been conducted to explore the existence or properties of wormholes? I'm quite fascinated by the idea and would appreciate a more detailed explanation.