A rescue lifeboat is a boat

Boat

A boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...

 rescue craft

Rescue craft

A rescue craft is a boat, ship or aircraft used in rescuing.The most common are Lifeboat for Inshore and closer to shore rescues. For operations further out from shore helicopters & ships are mainly used....

 which is used to attend a vessel in distress, or its survivors, to rescue crewmen and passengers. It can be hand pulled, sail powered or powered by an engine. Lifeboats may be rigid, inflatable

Inflatable boat

An inflatable boat is a lightweight boat constructed with its sides and bow made of flexible tubes containing pressurised gas. For smaller boats, the floor and hull beneath it is often flexible. On boats longer than , the floor often consists of three to five rigid plywood or aluminium sheets fixed...

 or rigid-inflatable combination hulled vessels.
There are generally three types of boat, in-land (used on lakes and rivers), in-shore (used closer to shore) and off-shore (into deeper waters and further out to sea).