A drag (also called a ruff) is two grace notes followed by a main stroke — three notes total, but heard as a brief texture leading into the accent. The grace notes are a controlled double played by the lead hand; the main note is the opposite hand.
Think of it as a flam plus one extra grace: where a flam has one quick grace, a drag has two. A right drag is two soft l's leading to a strong R; a left drag is two soft r's leading to a strong L. The two grace notes are essentially a soft, controlled double — clean enough that you can hear two strokes, not just a buzz. That distinction is what separates a drag from a buzz-roll.
The technique trap: most beginners squash the two grace notes into a single bounce. Practice the grace alone first as a soft double — both notes equal, both audible — before you attach the main stroke.
Reading the Notation
The renderer draws drags as two small beamed grace notes before the main note. Each grace carries a lowercase sticking (l or r); the main note carries an uppercase sticking and an accent. The grace notes are not on the metronome click — the main note is. Don't try to play the two graces "in time"; play them tucked in just before the main stroke.