Welcome to... "Micro-Lesson 234"
The riff uses triad inversions based upon our 5th string for their lowest tones. This method of using chord inversions is quite popular and songs like the, "Red Hot Chile Peppers - Under the Bridge," apply this concept to their chord changes in that piece of music.
Triad inversions have three positions, they are the; "Root" "First" and "Second." The order is based upon which chord tone is in which position. If the First chord tone (the naming note) is in the bass, this is the Root Position. When the chords 3rd degree is in the bass, this is 1st Inversion. And, when the chords 5th chord tone degree is in the bass, we call that, the 2nd Inversion. The lowest tone of the chord can function within the bass at any point in time. The only rule is that if the chosen position produces an effect of nice voice leading between the chords, then it works, if it does not, try something else.
In measure one of this lesson, the first chord is an, "E Major." The third chord tone is in the bass, (G# = 1st Inversion). The second chord of measure one is an, "A Major." This chord has an, "E," in the bass, (2nd Inversion). Measure two of our riff begins with a, "C# Minor," chord in it's, "Root Position." The final chord of our riff is, "B Major," and this chord applies it's 3rd chord tone in the bass position, (D# tone). This would be another example of a chord in the "1st Inversion," just like our initial chord of, "E Major."
Take your time learning all of these fingerings if they are new for you. Over time they'll get easier. Be sure to work at using chord inversions in your own songs too. Enjoy the lesson!
Micro Lesson 234: "E Major" Triad Inversions Riff