when I look at my photo document there is an option under sharing called Zip. the description is 'to create a compressed folder that contains the selected items.'
so is that like a secret document being created that requires a password?
A ZIP file is a compressed file. Usually compression is used to make the file size smaller so that it can be e-mailed quicker or take up less room on a drive. Yes, you can password protect a compressed file, but that's not the primary purpose.
To use the file again, one must uncompress it with an appropriate application.
Other common compression / archive formats are RAR, ZIPX, ACE, 7Z and TAR. Windows likes to use CAB also.
Yes if you wanna extract files thats what zip is for if you want to play games and the file need to extract you click on the file zip thats holding all files in place to extract them.
Zipping a file (or more files) is a way to both bundle multiple files into one file and compress them so they take up less space.
Often when downloading software, you'll download one.zip file that can expand into multiple files to reveal the installer, which then you run setup.exe, or something.
The file can be password proteected if you want, but generally it isn't unless you have a reason to do so.