Neutron stars form in supernova explosions and/or by an accretion induced collapse of a white dwarf. At the time of their discovery – and for many years later – it was generally accepted that neutron stars can only be observed as pulsars. According to the source of energy they were split into two classes, i.e. being powered by either rotation or accretion. Today, the neutron star world is much more intrincate than it was fourty decades ago. In addition to the accretion powered pulsars, which are predominantly bright X-ray sources, and the rotation-powered pulsars which are observed throughout the electromagnetic spectrum, there are now X-ray Dim Isolated Neutron Stars (XDINs), “radio-quiet neutron stars”, Compact Central Objects (CCOs) in supernova remnants, Soft Gamma-ray Repeaters (SGRs) and Anomalous X-ray Pulsars (AXPs).