Shavuot is a 2-day holiday on which we celebrate our acceptance of the Torah on Mount Sinai. It begins at sundown on Tuesday, May 14 and continues through sunset, Thursday, May 16.
Literally translated as "weeks," Shavuot completes the counting of 7 weeks from Passover to the traditional start of the grain harvest. In Israel, it also marks the beginning of the spring Harvest festival. It is customary to eat dairy foods during the holiday.
For ideas on how to celebrate with children, check out suggestions from PJ Library here.