This is a group of insurers or re-insurers who insure particular types of risks. Claim payouts, expenses and premiums are shared in agreed-upon amounts.

This is not to be confused with co-insurance where one insurer takes the "lead" in a particular piece of insurance and other insurance companies participate in the policy.

Of course the other type of pool is a swimming pool. You will always have a degree of responsibility for injury to others when you have a pool. This is why the insurance companies will want to know exactly what you are doing to minimize the risk. As well you will be charged a liability premium. The value of the pool will be added into your home insurance and you will pay more on that portion of your insurance as well.