The Counting (Sefirat) of the Omer
 

In the days of the Temple, the Jewish people would bring a barley offering on the second day of Passover. This was called the "Omer" and in practical terms would permit the consumption of recently-harvested grains. Starting on the second day of Passover it is a mitzvah every day to "count the Omer" during the 50 days leading up to Shavuot. This is an important period of growth and introspection, in preparation for the holiday of Shavuot, when the Jewish people stood at Mount Sinai to receive the Torah

The Omer is counted every evening after nightfall. If a person neglected to count the Omer one evening, he should count the following daytime, but without a blessing. To properly 'count the Omer,' you must say both the number of days and the weeks. For example: "Today is 33 days, which is 4 weeks and 5 days of the Omer." Before counting, say the following blessing: Baruch ata Adonoy, Eloheinu melech ha-olam, asher kid'shanu be'mitzvo'sav ve-tzivanu al sefirat ha'omer.