mainframe computers

what is a mainframe ?

Mainframe computer are large, expensive computers that can support many users at the same time. Big organisations use mainframes to run their most important jobs. The term mini computer is used to refer to smaller mainframes.
supercomputers are the fastest of all computers.They´re needed where vast numbers of calculations are carried out, for example, in wheather forecasting. Supercomputers run a few programs very fast rather than running lots of programs at the same time.
what is a mainframe?