Q: Error Codes

Well, there are a couple, depending on what you are doing. Since you posted this in the iTunes section, this support document addresses update and restore errors for the iOS devices. Resolve iOS update and restore errors - Apple Support

Here is one that seems to be unique to Windows. iOS: Unknown error containing '0xE' when connecting to a Windows PC - Apple Support

And this one is for iTunes errors. iTunes: Possible iTunes Store errors - Apple Support

You can search the support section of this website for any additional ones if you like.

I'm not sure there is a single page that gathers all of the error codes together in one place. Usually the error code and the text of the message will locate a relevant support article. What is the error you are seeing?

tt2