A Star is a type of entity that, along with Planets and phase space, make up all of the locations in Sins of a Solar Empire. The star acts as the head of its solar system, as each solar system must have one and only one star. In maps with more than one solar system, they are the main -- and usually the only -- method of traveling between systems. With the correct research, ships are capable of jumping from one star to any other star, and there is no way of disabling this behavior. Star spawning is controlled through the GalaxyScenarioDef file.
In addition to their role in inner solar system travel, stars may also have passive abilities. They are also the only Sins location by default to allow players to construct more than one Starbase.