Help me understand these memory statistics from Process Explorer

Answer 1

From here:

The working set is the set of memory pages that were touched recently by the threads in the process. If free memory in the computer is above a threshold, pages are left in the working set of a process, even if they are not in use. When free memory falls below a threshold, pages are trimmed from working sets. If the pages are needed, they will be soft-faulted back into the working set before leaving main memory.

[Private bytes are] bytes, that this process has allocated that cannot be shared with other processes.

What "peak" means in that context should be obvious.