Where things can get tricky is when you need to save the file in a different format. The most commonly used file formats are explained in my article, Which Graphics File Format Is Best To Use When?
When you finish editing an image in Elements and go to save your changes, there are a couple of options which are unique to Photoshop Elements. You are given the option to include the edited image in the Organizer and to save your file in a "version set" with the original photo. When a version set is created, the edited file is saved with a new name, and it is displayed in place of the original photo in the Organizer, but your original photo is not overwritten or changed in any way. In Organizer, you will see the most recently edited version, but all previous versions are available for viewing, and you can even revert to a previous version at any time. In the Organizer, version sets are indicated with an icon in the top right corner of the thumbnail.
If you're saving an image intended for the Web, it's best to use the Save for Web command (Alt-Shift-Ctrl-S on Windows or Option-Shift-Command-S on Mac). The Save for Web command is specially designed for saving Web images, which you generally want to keep as small in file size as possible. Save for Web allows you to adjust various settings and save your images out to several Web-friendly formats. When saving your class assignments for these lessons, get in the habit of using the Save for Web command since your assignments will be posted to the forum.
We'll look at the save for web dialog box next.