OSNews

"If you're doing any kind of animation or running a process that needs to poll another process or a particular piece of hardware on a regular basis, you need an accurate timer. Depending on your application, the timer might need to be accurate to within one second, or within a fraction of a millisecond. If your timer's resolution is too coarse or its margin of error is too large, your animations will appear jerky or uneven, and your program that's collecting data from custom hardware will miss data or will fail altogether. Windows has two primary methods of measuring elapsed time, and two ways to provide periodic events."