What is a pure demand paging?

When starting implementation of a process with no pages in memory, the operating system sets the instruction pointer to the first instruction of the process, which is on a non-memory resident page, the process immediately faults for the page. After this page is brought into memory, the process continues to implement, faulting as necessary until every page that it requires is in memory. At that point, it can implement with no more  faults. This schema is pure demand paging.