The Queen bee is a fully-fertile female that only produces eggs. Laying eggs is her job -- her only job. But what makes a Queen a Queen? Royal jelly. Queens grow from larvae that is fed a special food called “royal jelly.” According to Wikipedia, royal jelly is secreted from the glands in the heads of worker bees. When worker bees decide to make a new Queen, they choose several small larvae and feed them with copious amounts of royal jelly in specially constructed Queen cells. This type of feeding triggers the development of Queen morphology, including the fully developed ovaries needed to lay eggs.
There is usually just one Queen bee per hive. If more than one Queen exists in the hive, they will fight to the death. Unlike worker bees, the Queen’s stinger is not barbed and she is able to sting repeatedly without dying. Once a single Queen emerges, the bees will follow and fiercely protect her.