Basics
How a chord is built
A chord is notes stacked in thirds; the arpeggio is those same notes played one at a time.
Take a scale and stack every other note: start on the root, skip one to reach the third, skip one more to reach the fifth. Root–third–fifth is a triad, the smallest chord.
The gaps are measured in tones (T, 2 frets) and semitones (½, 1 fret), the same ruler as the scales. A major triad is the root, a major third (2 tones / 4 frets) and a perfect fifth (3½ tones / 7 frets). A minor triad flattens that third to a tone and a half (3 frets). The third is what makes a chord sound bright or dark.
Stack one more third and you get a four-note seventh chord. Gypsy jazz lives on these four-note colours (6, m6, 7, maj7) rather than bare triads.
An arpeggio is the exact same notes, played one after another instead of together. Learn the chord and you already know the arpeggio: that's why chord shapes and solo lines connect on the neck.