Chords are very common musical features found in pop music but also in classical music. A chord is a pair or group of notes played simultaneously, making a harmonic sound. Often chords are played and held down in the bass clef while the melody part of a song is played in the treble clef.
There is some common and beautiful sounding chords that create beautiful harmonies. The most common ones that are good to have strongly in your repertoire and muscle memory are shown above. Go and try playing them for some beautiful harmonies!