Save VERSUS Save AS

Save and Save As
When you use the Save command, you save your work under it’s current file name. If you’ve never saved whatever it is you’re working on before, then you’ll get an opportunity to name it.
When you use Save As , you get a chance to save what you’re working on as a new file.

Here’s an example. Let’s say you’re working on a word processing document. It’s a new document and you decide to save it. A box comes up that lets you give it a name. Now, let’s say you add something to it. If you use the Save command again, it simply saves it with no questions asked under the existing file name. It replaces the prior version with this edited version.

OK, now let’s say you make a modification to the file, but you want to keep the original version as well. This is where you use Save As. When you use the Save As command, it allows you to save your current file as a new file with a new name. Now when you go to open your files, you’ll find you have both the original version and the new, Saved As version.