I’ve highlighted A for particular attention here because it’s such a nice key on the guitar ... root-3rd-5th-maj7 (A-C#-E-G#) ...

Guitar skills: 'Add’ chords come in the form of either ‘add9’ or ‘add11’. The name tells you to add either a 9th or 11th interval to a basic major or minor chord. So, Cadd9 is a C chord ...