Then skip to the Recommendations . They can run at various resolutions and refresh rates. 640x480 just means that 640 pixels are fit across the top of your monitor and 480 up and down. You can fit more objects on a screen when it is in a higher resolution.
Larger monitors are better for running at the higher resolutions.
If you run a high resolution on a small monitor, the text may be hard to read because of its small size, despite the clarity. But, if your video card is producing a bright detailed picture and your monitor is dim and blurry, the picture will come out the same way.