Multiprocessors are processors made of two or more processing subunits; single computers containing more than one processor. There is no one model or configuration for these. The term's meaning varies with context, mainly by how processors are defined or implemented: many cores on one chip (multicore), many chips in one chip carrier (package), many carriers on one board, many boards in one system unit, many system units in one room, many rooms in one building, etc. Key trait: all subprocessors are treated, and work, together in some manner, as one processing unit, during some task. This is well suited to problems that can be processed as Multiple Instruction, Multiple Data: MIMD.
Some single personal computers now have two or four processors. Giant single supercomputers can have 64,000 (Connection Machine) processors, or more.