Why and how?
Sometimes we use the same symbols over and over in different documents. It might be easiest with some of these symbols to store them in a ‘symbols’ document. You should use the native format for whatever software you are using, i.e. if using illustrator use an .ai file. You could store this symbols document on the desktop.
Why use this approach?
Most software has more sophisticated ways to store symbols, the downside to these are that they are a little complicated. This approach is super simple.