This seven-day feast begins on the day following the start of Passover. In the haste of the Israelites to leave Egypt, there was no time to add leaven (yeast) to their bread. During this time, remembering the hardships in Egypt and how God freed them from captivity, the Jews eat nothing leavened.
The unleavened bread represents Yeshua (Jesus) sinless life; he is the only perfect sacrifice for our sins.
In John 6:35, Jesus boldly states that he is the bread of life. Not only does he remove our sins, he nourishes our souls!