According to Wikipedia a chord is:
“any harmonic set of pitches consisting of two or more notes that are heard as if sounding simultaneously”
In other (more simple) words, a chord is a group of notes that is played simultaneously to produce a pleasing sound. There are many different chords, from two-note chords to seven-note chords, the most popular being the triads, that is, the ones including three notes.
So now that we know what a chord is, what about learning how to play one.