Assembler:Programming Language Translator
An Assembly Language which is basically MNEMONICS like GO ,HALT, JUMP, NOT code which is translated to Machine Language by Programming Language Translator i.e Assembler.
So Assembler is a program that takes assembly and converts them into pattern of bits that the computer processor can use to perform its basic operations. This pattern of bits is basically Machine Language.
Examples of Assembler are
-NASM and -MASM