The instruction "MOV A, 5" is a command used in assembly language programming, specifically in microprocessor architecture. It means to move the value 5 into the register A. Registers are small storage locations within the CPU that hold data temporarily for processing. This operation is fundamental in programming, as it allows the CPU to manipulate data. By placing the value 5 in register A, the program can later use this value for calculations or comparisons. The MOV instruction is essential for data transfer between registers and memory in assembly language.