Assembly is a method for communicating with computers. Because computer just understands the binaries, 0s and 1s.
Assembly refers to the use of instructions that have a direct one-to-one mapping to the processor's instruction set ( no layer of abstraction between code and processor)
How programs interface with OS and processor
How data is represented in memory and other external devices
How the processor accesses and executes instruction
How a program accesses process data and external devices.
It requires less memory and execution time