Compilers are pipelines with a serie of step. Each step transform the input and provides data to the next.

Each step has then a contract with the input provided and its output 😃

The author goes in depth.

We can completely segment one component of the compiler from another by having the right form of data structure in between them. To build that data structure, you don’t need to know anything that happens to it afterwards, you just need to know what it means.