A more thorough explanation:

Definition: Joint and several liability is a legal concept where two or more parties are held responsible for a harmful act, and each party is independently liable for the full extent of the injuries caused by the act. This means that if a plaintiff wins a money judgment against the parties collectively, the plaintiff may collect the full value of the judgment from any one of them, who may then seek contribution from the other wrong-doers.

Example: Suppose that A, B, and C negligently injure V. V successfully sues A, B, and C, for $1,000,000. If the court used a joint and several liability system, V could demand that A pay V the full $1,000,000. A could then demand contribution from B and C. However, if B or C could not pay, A would be stuck paying the full $1,000,000.

Explanation: This example illustrates how joint and several liability works in practice. In this case, all three parties are held responsible for the harm caused to V, and any one of them can be made to pay the full amount of damages awarded by the court. This system reduces the risk for the plaintiff that one or more defendants are judgment-proof by shifting that risk onto the other defendants. However, it can also cause inequities, particularly where a relatively blameless defendant is forced to bear the financial burden of an incredibly guilty co-defendant's insolvency.

Other Varieties: There are other types of joint and several liability, such as market share liability and the doctrine of alternative liability. Market share liability is invoked when a good causes an injury, and there are multiple manufacturers of the good. The manufacturers will be held proportionately liable in accordance with their market share in the market of the good. The doctrine of alternative liability applies when it is impossible to tell which tortfeasor caused the plaintiff's injuries. Two independent tortfeasors may each be held liable for the full extent of the plaintiff's injuries, and the burden of proof will shift to the defendants to either absolve themselves of liability or apportion the damages between themselves.