Power chords are very similar to barre chords. As you remember, barre chords (and other chord formations) are comprised of R-3-5. Power chords are simply R-5. Power chords are not considered true chords since they lack the 3rd and are called dyads. It makes sense, dy meaning 2.
A lot of modern rock songs use power chords so you will see them come up in the songs later on. They are much simpler and they sound great. Don’t forget to practice your other chord formations also! Below are some examples of power chords.