What's the significance of a "Joint & Several" clause in a lease?

Answer

If an agreement states that you and your roommate(s) are "jointly and severally liable," it's confirming that you're individually and collectively liable for the entire rent. In the event that your roommate(s) fail(s) to pay, you can be held responsible for his/her portion of the rent. This "joint and several" liability continues throughout the stated life of the contract.