On the night of Shavuot, there is a very beautiful custom which is referred to as Tikun Leil Sahvuot, when we symbolically “complete” the entire Torah. Literally, the word Tikkun means “Repair,” and on Shavuot we are in some way repairing our connection to Torah. It could be that if we missed a Torah portion during the year, we can make it up on the night of Shavuot. Or the Tikkun could be about our commitment to Torah. On the night of Shavuot, we strengthen our love and commitment to the Torah and for that reason we try to learn the entire thing.