I don't generally use Wikipedia as a primary information source, but sometimes they offer a concise detailed explanation. Today is Passover, and you'll find the story and the Seder practice might awaken new thoughts and experiences for your Holy Week and Easter.
Here are a few teasers from the link:
"The rituals and symbolic foods associated with the Seder evoke the twin themes of the evening: slavery and freedom."
"The Four Cups represent the four expressions of deliverance promised by God in Exodus 6:6-7: 'I will bring out,' 'I will deliver,' 'I will redeem,' and 'I will take.'"
"Why is this night different from all other nights?"
Part of the song/recitation: "I love the Lord, for he heard my voice; he heard my cry for mercy."
And we cried unto the Lord, the God of our fathers, and the Lord heard our voice, and saw our affliction, and our toil, and our oppression. And the Lord brought us forth out of Egypt with a strong hand and an outstretched arm, and with great terribleness, and with signs, and with wonders... Deuteronomy 26