Stride — the Harlem left hand (James P. Johnson, Fats Waller, Willie "The Lion" Smith) that is the rhythm section: a bass note on 1 and 3, a mid-register chord on 2 and 4, the hand striding across the keyboard between them. Transcribed from Scivales' Jazz Piano: The Left Hand, Part I, Ex. 3-1 — a cycle of dominants (E7–A7–D7–G7, "Sweet Georgia Brown" changes) where the bass note on beat 3 is the chord's tritone (Bb under E7, Ab under D7) or its third (C# under A7, B under G7), and the chords are three-note shells (3rd, 7th, root or 3rd) that sit just below middle C.
The right-hand staff is empty on purpose: that is where the tune goes. The chords on 2 and 4 are the "back-beats" Scivales names in Part I — the hi-hat marks them so you can hear the stride as a drum pattern.
Listen for the alternating bass: root, then the "wrong" note that pulls to the next root. Practice: slowly, eyes on the jump; the chord must not be louder than the bass note. Compare swing-lh-shells (the bebop left hand that replaced stride) and boogie-woogie-lh.