A.L.U. stands for Arithmetic and Logic Unit. It is the core part of the CPU - central processing unit. ALU is the set of chips, electronics hardware, that performs logic and arithmetic operations on numbers in the binary system with radix 2. It understands only 0 and 1.
ALU performs additions , multiplications, AND, OR operations or inputting a data from memory or a device or outputting result to memory or device. All software that runs on computers, is a set of instructions to the processor. ALU executes all the instructions.
Each type of ALU has a specific machine language.