Welcome to... "Micro-Lesson 251"
This riff is made up of three primary chord positions, including; a third position "G" triad and two open position chords of "C and G."
The first and second measures cover a fingerpicked idea through a small 4th string root "G Major" triad in the 3rd position. This "G Major" triad applies a few different tones used off of the 2nd guitar string. The "G" chord is modified from the triad to a 6th chord and back. It is a simple concept, but one that highlights a nice melodic touch through the harmony.
In measure three the "C Major" chord appears and applies an arpeggiated concept across the chord outline with an added grace-note hammer-on upon the 3rd string. Watch the execution of that hammer-on. It must be performed very quickly, so as to not justify the grace-note's use in time.
In measure four, the "G Major" chord appears once again to resolve the fingerstyle melody line. This time the "G" chord appears in the open position with an added 3rd string "A" upon the third beat of the measure. This introduces the sound of a "Gadd2" chord. While this chord only appears for a brief moment, it certainly colors the sound of the measure and offers a unique sound to our fingerstyle guitar part.
Use standard folk fingerpicking approach or Classical Guitar technique to perform the part. Enjoy!
Micro Lesson 251: "G Major" Folk Fingerpicking Riff