This annual feast was celebrated in conjunction with Passover. In remembrance of God's bringing them out from slavery, they were to eat unleavened bread for the seven days beginning with Passover and to even remove it from their homes for that period of time. In his commentary on the book of Exodus, David Guzik said that it showed the purity Israel was to walk in, illustrated by eating only bread without leaven, after the blood-deliverance of Passover. On the seventh day there was to be a feast showing that a walk of purity in the Lord is a life filled with joy. They were reminded to tell their children why they did this.
So many of us pay little attention, equating the feasts with just another piece of Old Testament history, not very relevant to our lives today. But I beg to differ. The feasts remind of us of God's loving care for us and point us to Jesus.
The Lexham Bible Dictionary says it best.
During Jesus’ final celebration of the Passover and Feast of Unleavened Bread, He equated the bread with His body and the wine with His blood (Matt 26:26–29; Mark 14:23–25; Luke 22:19–20; see also John 6:30–58). Because this commemorative meal was meant to recall the first Passover, Jesus was identifying His blood with that of the Passover lamb, whose blood saved the firstborn of Israel, and His body with the unleavened bread that sustained the people as they escaped from slavery (see Stein, Luke, 540). The next day, Jesus died on the cross as the lambs were slaughtered for the Passover sacrifice, leading to the interpretation that "Christ, our Passover lamb, has been sacrificed." (1 Cor 5:7 NIV)
Next up, The Feast of Weeks (Pentecost).