Different file formats cater to the needs of
different applications. The file format you choose depends on the
content of your image and how you plan to use it. For example,
you're saving an image for use on the Web, you should choose JPEG,
GIF, or PNG format.
You can save individual images in different
formats using File > Save As. You can convert several images to the
same file format, or the same size and resolution, using the Batch
command.
Until you've finished creating an image and
have decided how you want to use it, you should save the image in
Photoshop format (PSD) which is the default file format. Saving your
image in the Photoshop format guarantees that you will be able to
access all of the image data when you reopen the image.
If you choose a format that does not support
all of the data in an image, a warning appears at the bottom of the
Save As dialog box. If you see this warning, save a copy of the file
in Photoshop format in order to support all of the image data.
in the shortcuts bar.