Entity is a term which refers to an institution, organization, or being that has its own separate legal existence or tax purpose. An entity usually has its own identity which is separate from its owners or members. A corporation is a good example of an entity.
Other examples of entity include partnerships, government agencies, estates, trusts, etc. Entity is treated more like a person, and just like a person, an entity can make its own decisions, be sued, form partnerships, and function legally.