Photoshop increase file size

[Paul MR]

Metadata is information that is stored within the file, this information is generated by your camera.
The information can be viewed and some parts can be added/amended or removed.

To view the information in Photoshop
Open a photo, then File - File info...

Metadata can be very useful IE:
Add copyright information
Add keyword(s) so that the these can be selected/found in Bridge etc.
You can add information on where you took the photo/ by whom/ telephone number(s)/ Web sites. All sorts of information of your camera. etc. etc.
There are some cameras that will add GPS information so you know exactly where the photo was taken.

[Steve]

Photoshop Save for Web CS3 or previous versions stripped the exif from the file, Photoshop CS4 and CS5 are different, only if you select NONE will the exif and PPI information will be stripped..

Thanks Paul.
I'm not a web guy so I use Save for Web for an occasional animated GIF.
The option to strip the exif data was right there but it didn't click with me.