The closest stars to the Earth are also some of the best studied celestial objects. In Astrophysics, distance makes all the difference. The closer an object is, the more light we will be able to glean from it. Stars come in different types (masses, chemical compositions, ages), but the closest example of each type will be a critical object to study. In this article we review five fast facts about the closest systems to the Earth and what they mean for astrophysical studies.