We celebrate Lag BaOmer on the day Rabbi Shimon Bar Yohoi died. Before he died, he hid in a cave for twelve years with his son, Rabbi Elazer where they studied Torah day and night. During this time of study they also created a book called The Zohar (Kabbalah) Which revealed some of the secrets in the Torah. A person is not allowed to study the Zohar  if one had not studied the Torah, Talmud, Shulchan Aruch and all the commentaries. If one has studied these then they may study the Zohar. When the Romans found out that Rabbi Shimon Bar Yohoi was hiding and was learning with a candle, they went out on a search for Rabbi Shimon Bar Yohoi’s fire but when they went out to search all the jews had lit fires to confuse the Romans so they wouldn’t be able to find him. This is why some people light Bonfires as a custom on Lag Baomer.