An assembler is a program that accepts ASCII text as input and produces a machine language program. Instructions of the computer are given short, mnemonic (memory helping) codes like ADD, SUB, and JMP so that programmers do not have to remember their numeric equivalents. Even better, sections of memory can be given labels that are not only easier to remember but more descriptive and which can "move around" in memory as the program grows or shrinks.

We call this programming language assembly language, assembler, or assembler language. All terms mean the same thing.