Who is Dionysus a.k.a. Bromius, Evius, and Bacchus (from The Baccha from Euripides V and what is their importance?

Dionysus is Zeus' son. His mother is Semele. Hera, enraged by Zeus's infidelity, killed Semele during childbirth. Zeus, however, saved Dionysus at the last minute. Dionysus is the god of wine and dance.

Over time, rumors abound that Zeus was not his father, and the people of Thebes have stopped worshiping Dionysus, believing him to be a false god. As a result, he travels to Thebes in disguise, planning to make Thebes suffer for its blasphemies. He turns all the women mad, destroys Pentheus' palace, and casts a spell over Pentheus that causes him to dress like a woman and go to the mountain. The women, led by his mother, tear him to pieces.