The period between the beginning of Passover and 'Shavuot' (Pentecost) is a period of counting. Every evening, Jews count the days and weeks that have passed since the first day of Passover. This counting is called the 'Sefirat HaOmer' - the counting of the 'omer.' 

Before analyzing the nature of this connection between Passover and Shavuot and the significance of the counting of the omer, we will first probe some of the laws relating to the counting of the omer and their textual sources.

Why do we count forty-nine days between the offering of the omer and the bread offering? The commentators offer different explanations.
 

Courtesy of the Virtual Beit Midrash, Yeshivat Har Etzion