Have you ever had some web page, or something you wont be able to access later up on your mac that you wanted to share via email, or keep for later and not know how to save it? What you can do is take a screen shot. A screen shot is a image generated by your computer of everything that is showing on your screen at the moment.
To take a screen shot press Command-Shift-3. This will save it on the desktop with the file name being a timestamp. If there are parts of this image that you want to crop such as sensitive information you can edit it quickly in preview. All you have to do is highlight the section you want to crop out. Then you press delete and the section will be come grey like the background.
A similar command that you can do is Command-Control-Shift-3. This will copy the screen shot to the clipboard. You can then paste the image into any image editor that you use.
An alternative way to only capture nonsensitive information is to take a screen shot of only a selection of the screen press Command-Shift-4. Then you select the section that you want to take an image of. This will also save to the desktop with a timestamp for the name.
In the same way as before you can do copy a selection of the screen to the clipboard using Command-Control-Shift-4.
To take a picture of only one open window do the same as above Command-Control-Shift-4, then press the space bar, then click the window that you want.
To save the files that you have created open them from the desktop in preview (which is the mac default if you haven’t changed it.) In preview you can “save as” the file on the desktop, changing the folder its in, the name, and the file type. (Preview has 12 different file formats to choose from)