The workers are unloading the goods from the truck.
Tips
grammar
卸 = to unload / remove; 掉 here is a resultative complement meaning "away / off / completely", as in 扔掉 (throw away), 删掉 (delete). 卸掉 = thoroughly remove. Compare with 卸下 (xièxià, to take down — emphasizes setting it down somewhere).
