Aliases are basically just a pointer to another file.
You've probably put a few aliases in your apple menu folder of some of the programs you use most often. But that is just the beginning of what you can do with aliases. For example, I put an alias for my hard disc in my menu folder. Because of the hierarchical menu sytem, I can navigate through my hard disc without wading through all those windows. Then when you want to check your pages, you can easily get to them from the open file command in the browser's file menu.