Protection and indemnity insurance, more commonly known as "P&I" insurance, is a form of mutual maritime insurance provided by a P&I Club. Typical P&I cover includes: a carrier's third-party risks for damage caused to cargo during carriage; war risks and risks of environmental damage such as oil spills and pollution.
A P&I Club is a mutual insurance association that provides risk pooling, information and representation for its members. Unlike a marine insurance company, which reports to its shareholders, a P&I club reports only to its members. Originally, P&I Club members were typically shipowners, ship operators or demise charterers, but more recently freight forwarders and warehouse operators have been able to join.
Whereas the assured pays a premium to an underwriter for cover which lasts for a particular time (say, a year, or a voyage), a P&I Club member instead pays a "call".  If, at the end of the year, there are still funds in the pool, each member will pay a reduced call the following year; but if the Club has made a major payout (say, after an oil spillage) club members will immediately have to pay a further call to replenish the pool.