The Haggadah is a small book that is used at the Passover table each year. It contains the order of the Passover seder and is used by the seder leader and participants to conduct the rituals of the meal. The Haggadah also recounts the story of the Exodus, when the Israelites were freed from slavery in Egypt. It contains poetry and songs that have become a part of Jewish tradition as well.
According to Alfred Kolatch, author of “The Jewish Book of Why,” the Haggadah was introduced by members of the Great Assembly 2,500 years ago in order to meet the requirements of Exodus 13:8, which states: “And you shall instruct your son on that day….” The Great Assembly was a group of the most learned rabbis of the time. The Haggadah fulfills the requirements of Exodus 13:8 because every time it used it reminds us of the Exodus story and teaches the younger generations about Passover. Haggadah literally means "telling" in Hebrew. In other words, the "telling" of the Passover story.
There are many different versions of the Haggadah. Haggadot (plural of Haggadah) have been published in nearly every country where large communities of Jews have lived. For this reason haggadot often reflect the customs of the communities they originated in, the end result being some variation between one haggadah and another.