Chapter 5 is about processes.
It introduces the structure of the memory and its sections, such as the stack and the heap.
It also introduces the resources of a process, such as open files and process states; and the process hierarchy on UNIX systems.

Chapter 6 is about the virtual memory.
It introduces the concepts of pages and frames, how virtual memory addresses are translated to physical memory, etc.

The book is really a introduction to computer science for the novice.
A lot of the stuff there I have already seen in my CS course or I'm seeing right now.
It's good to review those stuff though.