What Do Those Symbols after the File Name Mean in Photoshop's Title Bar?
Somewhere along the path from being completely intimidated by Photoshop to learning how to use it you will likely notice that occasionally there's a funny punctuation symbol after the name of your image in the title bar. It isn't always there, and it isn't always the same thing. But when you've got one, it isn't all that obvious what it means.
For every image, Photoshop adds several helpful pieces of information in parenthesis following the name of the file being edited. First comes the color mode for the image being edited. For most of us this will likely say RGB, but it could be CMYK, Lab or "Index" for GIF files or other indexed color formats. This will be followed by a slash and a number representing the bit depth for the image, typically either 8 or 16, but perhaps more now that Photoshop supports 32-bit HDR images. For many files, this will be everything contained in the parenthesis, but for some there may be more.
That "more," if a particular image has one, will be one of two punctuation marks, either an asterisk or a pound sign (number sign).
If you see an asterisk (*), it means your image is in a color profile other than your working space default. If your working space is Adobe RGB and your image is too, then no asterisk, but if instead you open a file in sRGB, it will have an asterisk at the end of the title bar information to let you know about the profile mismatch. This isn't a bad thing necessarily since you could easily have opened it this way on purpose. Photoshop is just subtly letting you know about the situation.
If instead you see a pound sign (number sign, #), it means your image has no color profile associated with it. More than likely, this is a bad sign if you are editing an image you care about. Photoshop is not color managing the image so what you see on the screen may not accurately reflect what the image actually looks like. You should use the Edit >> Assign Profile menu command to assign the correct profile to the image. If you don't know what the profile should be, backtrack to where the image came from to see if you can figure it out, whether that source may be your camera or your friend.
What these symbols mean used to be better documented back when color management was new in Photoshop. So much has been added to Photoshop since then though that this information often seems lost among everything else Adobe has to now document. Photoshop is a big program and it's not always easy searching for a few punctuation marks in the help files. But now you know.