Answer by KylePolansky · Sep 04, 2011 at 10:12 AM
The registry is in simple terms a place where lots of different settings can be stored. You can explore the registry by going to run (windows key + r) and typing in "regedit.exe". Be very careful NOT TO CHANGE ANYTHING, as this might give you more registry errors. I do not have a Mac, but I think I have heard that they mostly use .ini files. These are files in the file system that have all of the programs settings in them. They are nice because with a simple copy, you have all the settings for your computer, without having to do a registry backup, which contains other stuff as well.
Answer by augustuen · Sep 04, 2011 at 11:20 AM
In Mac OS X all apps are contained in special folders with the file ending .app with all the files and resources that the Application uses (like images, settings, etc.), Finder reads a small file that tells it which application to run when you click on these "folders".
Mac OS X does have something similar to the registry: /Library.
Answer by Joel · Sep 04, 2011 at 08:43 PM
The Windows registry is just a big database of settings for Windows and many other programs. Older software (including the Windows OS) used .ini files before the registry. A registry error can be an entry that is pointing to a nonexistent file. This type of "error" is very common and should not concern you at all. Some software will make you pay money to fix these "errors", but it's not worth the money.
(I'm no expert at the Mac OS) The settings for applications are stored in the .app. A .app is a special folder that contains multiple files, but will open like an executable by default. I think some system settings are stored in the /etc/ directory in .conf files (that's the way many *nix applications store info).