Hey I am attempting the self-taught thing.

I'm getting some guidance from a friend who is a good player and I have to say I'm very happy with my progress.

My question is this. My friend gave me two new chords to learn a major 7 and e2

I cannot find any clear definition on YouTube or otherwise of what e2 is.

I have one of those laminated guitar chord references and it's different then what I see.

Also there are so many references to chords fingered in alternate ways and some just seem to make a completely different sound than other references. This makes it very confusing. Are there any gold standard references out there?

Thank you in advance.