Chords are a combination of three or more notes, that sound good together.
When strumming a guitar we play chords. First chords you learn are usually pure major or minor chords, that contain only three notes (triads), that are doubled in two octaves.
Harmonizing a scale means building chords starting from each of its notes. That implies there are seven chords in a diatonic (seven note) scale.
Most songs in western music are just a sequence of chords selected from the Major Scale.
To build a triad (3 notes chord) from notes in a scale select any scale note as root (also gives the name of the chord) then select every other note (jump one note and pick the next) until you have three notes.