In a nutshell
The control unit is the part of the CPU that turns an instruction into the right sequence of control signals — the on/off lines that steer data through the hardware. There are two ways to build it. Hardwired control uses fixed logic gates wired to the opcode: fast and cheap, but changing it means redesigning the circuit. Microprogrammed control stores the signals as a tiny program in a control memory that a microPC steps through: slower, but easy to extend or patch.