You can read about it from the site Judaism 101 here. (Obviously, this is a Jewish site which denies the Christian interpretation - don’t let that phase you, though. It’s generally good info.) You might also re-read Exo 12.
The Paschal meal is highly significant for Catholics, as it pre-figured the mass (where we truly eat the Lamb - again, Exo 12). The 4 questions asked during the haggadah are also significant - particularly the question of the “wicked child”, which highlights the anamnesis (bringing to the present the past reality) inherent in the Paschal mystery.
To understand how this played a significant role in early Christian thought/writing, you might check out Scott Hahn’s article in This Rock, entitled “The Hunt for the Fourth Cup”. After reading it you should have a better understanding, and perhaps some more questions.
Oh, and you might want to keep in mind that since the destruction of the Temple (roughly 70AD) and the elimination of the Aaronic (Jewish) Priesthood, there’s no properly slaughtered lamb in Judaism any more for their Passover meals - Biblically speaking. Bless their hearts, they’re merely doing the best they know how.
You might notice some eerie parallels with our Liturgy…like the following:
Blessed are You, L-rd, our G-d, King of the universe, who has sanctified us with His commandments and commanded us concerning the washing of the hands.
Blessed are You, L-rd, our G-d, King of the universe, who brings forth bread from the earth.
Blessed are You, L-rd, our G-d, King of the universe, who creates the fruit of the vine.