Exodus means a going out. Broadly speaking this second Book of the Pentateuch teaches that redemption is essential to any relationship with a Holy God. As Exodus shows us even a redeemed people can not have fellowship with God unless they are constantly cleansed from the defilement of sin. Answered prayer is dependent on purity. (Psalm 66:18)
Exodus also presents Moses as a mighty intercessor. The powerful intercessions of Moses were more than a match for the murmurings of Israel against their God.