in-struc-tion: a code that tells a computer to perform a particular operation
The intermediate representation (Tree) language expresses only one operation in each tree node: memory fetch or store, addition or subtraction, conditional jump, and so on. A real machine instruction can often perform several of these primitive operations. For example, almost any machine can perform an add and a fetch in the same instruction, corresponding to the tree
Finding the appropriate machine instructions to implement a given intermediate representation tree is the job of the instruction selection phase of a compiler. ...