Judaism helps us to understand our own Christian faith because it enables us to understand how and even why Christianity came into being. [The God [Yahweh] of Judaism is also the God of Christianity, and both covenants [the Old and the New] were established by Him.]
Importantly, Christians learn from studying Judaism, why it was necessary for Christ to die for us. Under the Old Covenant, sin had to be atoned for, and this could only be accomplished by the shedding of the blood of a pure and sinless animal. We thus come to understand how important blood sacrifices [for atonement of sins] really were in the sight of God, and why Jesus Christ had to be sent forth for this very reason.
Christians could appreciate God's idea love for those who have Faith in Him by reading about Abraham, progenitor of the Israelites. The Abrahamic Covenant [a Faith covenant] makes those who have faith like Abraham, co-heirs with Abraham, and thereby, recipients of the blessings that God promised to him. Christians who are not Abraham's natural descendants can receive the blessings promised to Abraham because of their Faith in God and Christ Jesus.