In computer architecture and microprocessor instruction, the Operand is the data is the data on which an operation is performed. In context to the mathematical operation, an operand is a quantity on which arithmetic operation is to be performed.
Microprocessor Instruction: ADD C ( it means add the content of register C to the accumulator). In this Instruction, the register C and Accumulator are operands on which the Add operation is performed. While the Addition operation is known as Opcode.
Mathematics or in C++: a = d / 2. In this example d and 2 are operands on division operation is performed.