the short answer
The barbell row is a compound pulling lift where you hinge at the hips with a flat back, hang the bar at arm's length, then row it to your lower ribs by driving your elbows back and squeezing your shoulder blades together. It builds the lats, mid-back, and rear delts in one movement. The single most important cue is to hold the hinged torso still and pull with the elbows, not heave the weight up with momentum.
This article is general technique education for coaches and clients, not medical or rehab advice - form is individual, and a qualified coach watching the movement and giving a form check is the gold standard. Clients with pain or a relevant history should clear it with a qualified professional first.