To make things more confusing, there's also a page file (sometimes referred to as a paging file). Each page is a fixed size (typically 4 KB on a Windows system). Windows organizes memory, physical and virtual, into pages. So why do people get confused over memory usage? One of the biggest sources of confusion, in my experience, is the whole concept of virtual memory compared to physical memory. Even with that workload, I still had roughly 10% of physical RAM available.
And, of course, three memory monitoring tools. At one point I had 13 browser tabs open, including one playing a long Flash video clip) at the same time I had opened a 1000-page PDF file in Acrobat Reader and a 30-page graphically intense document in Word 2010, plus Outlook 2010 downloading mail from my Exchange account, a few open Explorer windows, and a handful of background utilities running. Even on a system with only 1 GB of RAM, I found it difficult to exhaust all physical memory.
