Instruction_set is a group of commands for a Central Processing Unit (CPU) in machine language. The term can refer to all possible instructions for a CPU or a subset of instructions to enhance its performance in certain situations.
All CPUs have instruction sets that enable commands to the processor directing the CPU to switch the relevant transistors. Some instructions are simple read, write and move commands that direct data to different hardware.
Source: https://whatis.techtarget.com/definition/instruction-set