Phrases like `supercomputer' or `supercomputer on a chip' are quite widespread nowadays. The TOP500 gives us the instrument to analyse and define which machine can be called and which one should not be called a supercomputer. The TOP500 so far shows only MP vector computers or MPP systems. We do not think that the list will be restricted to these two classes in the future, especially high end multi CPU workstations will undoubtedly enter the list in one of the next releases. In this chapter we will first look at the different classes of computers and families of systems in the TOP500. We will then present the main technological and architectural features of each family shortly.