The B’nai Yisaschar, a chasidic work on the holidays, writes that the numerology of the 49 days of the Omer is contained in the phrase, "Lev Tov" a good heart, which is essence of the Torah. The first 32 (=lev, heart) days of the Omer we try to develop a good heart. Lag (=33) Ba’Omer represents the beginning of Tov = good. What is good? The light of creation and of Torah. Lag Ba’Omer is the start of the revelation of the light of the Torah which will be fully revealed at the end of the 49 days, on Shavuos, when we receive the Torah.