For questions about the theory behind building and naming chords. Do not use for questions about how to physically play a chord or chord progression on an instrument.
Chord Theory is the specifics of the construction, usage, function, terminology, and other details of the implementation of chords into musical harmony.
Chords make up a big part of the analysis, understanding, and how we convey harmony. There is a lot of theory that goes into how certain chords are named and what goes into building them. For more information, read the tag wiki for chords.
Theorists tend to follow specific naming conventions for different sonorities (groups of notes). For example, to describe many chord qualities, jazz musicians name the chord first based on the quality (or absence) of its third, then its seventh or highest natural extension, then any other altered notes. For different chord-inversions, classical theory ascribes the label root position, 1st inversion, 2nd inversion, all the way through the nth inversion, depending on what note is in the bass position.
See also What determines a chord's name? for an old chestnut of a question about chord naming.
For more reading, see the below links:
- https://nationalguitaracademy.com/chord-theory/ (a guitar-centric take on chord theory)
- https://www.musicgateway.com/blog/how-to/chord-music-theory (beginner fundamentals with some more specific examples for guitar)
- https://www.pianolessonsonline.com/chord-theory/ (a piano-based introductory theory page)