Some special ship abilities (cloaking, alchemy, ...) are keyed to various ship hull types. For example, in the standard ship list, only the Aries class ship can do advanced refinery.
In the original host, these abilities are hardwired to ship types.
In PHost 3.x, ship list designers can freely configure which ship does what. In addition, these abilities can be allowed to certain players/races only. PHost 4.x even allows hull functions tied to individual ships, and functions restricted by experience. See PHost hull functions for details.
Compare Racial Abilities.
