Unlike most other Jewish holidays, Shavuot has no specific Torah commandments for celebrating other than the traditional festival observances. However, because of its agricultural and spiritual significance, there are many traditions and customs surrounding the celebration of the holiday, like eating dairy and staying up all night to study Torah, a practice known as Tikkun Leil Shavuot.
Why dairy and why study Torah until sunrise, you ask? According to Midrash (ancient Biblical commentary), the Israelites went to bed early the night before receiving the Torah in order to be well-rested for the momentous day ahead, but then overslept and had to be woken by Moses. In order to atone for this national mistake, many Jews study Torah all night long, in symbolic anticipation for receiving the Torah on Shavuot day.