
This first set of 3 chords works very well for certain beginners. The reason may be that all four fingers are working at once. Sometimes this works well first, sometimes it might be better to use the common set that starts with E minor. You can also drop the pinky on the G and Cadd9 to simplify the fingerings.
These voicings of G, C, and D are wildly popular (as are versions of them - or changing elements). If we can play these chords, we can play a whole bunch of songs. Add in Em, Am, & Bm, and the library of possible tunes becomes immense.
We can use the Cadd9 anytime you see a C, whether we are in the key of G or not. It is also very common to hear these chords used with a capo, because they have sweet resonance. Try a capo at 3 (B flat, E flat, F).

This block of chords is a standard set of basic guitar chords. Some of the chords above have different fingerings and other versions. We chose a common way to play these most common chords.
When we see a chord symbol, it is up to us how you voice it (choose the voicing). We can even change the voicing of the same chord within its time frame (use 2 or 3 types of Em for a measure). We can also have changing elements (parts of the chord are changing - being melodic within harmony).

This is an alphabetical Dominant chord scale for the natural tone roots. These are all Major chords with a flat 7. Dominant chords are built - Root/Third/Fifth/Flat-7 [R-3-5-b7].
Dominant chords are typically only the FIVE chords in a Major key, yet in Major Blues, we can use all dominants.
Learn how those were created with EON. Once we know chords in a key, and what key a song is in, we can start to predict what might be used in a song.