What happened between the passover and pentcost?

In the Jewish tradition, the interval between the festivals of Passover (Pesach) and Pentecost (Shavuot) is known as the Omer, and is characterized by a special blessing said every evening counting the days between the two festivals. This is a period of spiritual preparation for Pentecost, a festival that remembers God's giving the Torah to Moses at Mount Sinai.