Analog computers are almost never used outside of experimental settings. A digital computer is a programmable clocked sequential state machine. A digital computer uses discrete states. The borders between those three terms are highly ambigious, non-contiguous, and erratically shifting. The processor is the part of the computer that actually does the computations.
Some computers have more than one processor.
This is called multi-processing . CISC stands for Complex Instruction Set Computer. Mainframe computers and minicomputers were CISC processors, with manufacturers competing to offer the most useful instruction sets. RISC stands for Reduced Instruction Set Computer. DSP stands for Digital Signal Processing.