Thousands of bonfires across the country tonight will mark Lag BaOmer, the 33rd day of the Omer period, remembering Rabbi Akiva, Rabbi Shimon bar Yochai and Bar Kokhba.
The minor holiday of Lag BaOmer, the 33rd day of the Omer period between Pesach (Passover) and Shavuot (Pentecost), commemorates three occasions: the end of a period of mourning for thousands of students of Rabbi Akiva who died in a plague, the anniversary of the death of Kabbalah-author Rabbi Shimon Bar-Yochai, and Bar Kokhba's revolt against the Romans.
Lag BaOmer is marked most notably with traditional bonfires throughout the country. A tradition kept by Jewish children of all backgrounds in Israel, the bonfires represent the light of Torah, and especially that of the Kabbalah, brought to the world by Rabbi Shimon.
Israel's Chief Rabbi Yonah Metzger, in his work B'Maagalei HaChayim, notes that the custom of playing with bows and arrows on this day is "apparently because tradition tied this date with the Bar Kokhba rebellion." A learned article on the subject by Rabbi Pinchas Stolper can be seen here.