What is Lag B'Omer
"Lag B'omer" is the thirty third day of counting the Omer. The word "Lag" means 33 because it is comprised of the letters "lamud" and "gimmel," corresponding to the numerical values of "30" and "3."
The Omer period is a time of heightened spiritual sensitivity and growth. The closer Shavuot draws, the greater our anticipation grows for the climactic celebration of the Giving of the Torah, the watershed event of Jewish history.
However, the greater the potential there is for growth and building, the greater the potential there is for destruction. Consequently, in eras when the Jewish People have not lived up to their potential, the Omer period has become one of tragedy.
In the time of Rabbi Akiva, who witnessed the destruction of the Second Temple and who was the greatest Torah Sage of his generation, twenty four thousand of his disciples died in an epidemic. The underlying spiritual cause of the epidemic was the students' lack of respect for each other. This sad event and others took place during the Counting of the Omer. As a result, the Omer period has become one of semi-mourning in which we don't hold weddings or festivities, nor do we shave or get haircuts. But because the epidemic was suspended on the 33rd day - Lag B'omer - Lag B'omer has become a joyous day of celebration.
After all his students died, Rabbi Akiva "started over" and began teaching other students. One of his foremost students was Rabbi Shimon bar Yochai, the author of the Zohar. The Zohar, which means "The Shining Light," is the basis of the secret teachings of the Torah. Some people light bonfires on Lag B'omer and sing songs in honor of Rabbi Shimon bar Yochai, who revealed the teachings of the Zohar to the world on Lag B'omer.