I am almost done with guitar fundamentals two. I remember one of those chords that have numbers in their description (E7 for example) have been mentioned in passing in the videos. and I dont know what they are. neither have I seen any lessons on them. I must have skipped it. or is it even covered at all? If it is can someone direct me to the video where it is taught..and if its not can you explain them to me pls :)

Thanks