What does it imply when applied to a computer that has a limited instruction set to use the word "reduced" in this context?

Match the vocabulary below with their correct definitions: the portion of an encoded instruction that tells the CPU what operation to perform a single operation of the CPU a value passed to a function in a high-level language a value that the CPU operates on when executing an instruction 1. Argument 2. Instruction 3. Opcode 4. Operand 5. Parameter 6. Prototype

What may possible trigger a return to the instruction presently being performed in the case of an error?

What does it mean when referring to a computer that has a restricted number of instruction sets to say that it is "reduced"?