What is the difference form a sting bee and a non sting bee?

A bee's stinger is modified ovipositor, the organ that a female bee uses to lay eggs. For worker bees, which are sterile, their ovipositor has evolved into a stinger only. For queen bees, the stinger does double duty as a stinger and an egg layer. Bees without stingers are most likely male.

If there exists species of stingless bees, then the ovipositor did not evolve into a stinger organ for those species.