The goal of the Old Law was, ultimately, Christ. He fulfilled everything that was written in the Old Testament
The Old Law is made of three parts:
1. Ceremonial - this includes all rules relating to worship - dietary laws, prayers, religious festivals etc.
2. Civil - which encompases all rules relating to state - criminal punishments, rules of trade, organization of government.
3. Moral law - law that is in the mind of a believer - mostly the Ten Commandments.
Ceremonial law was abrogated because all sacrifices point towards Christ, civil law was abrogated because the "kingdom" that Jesus talked about is no longer the physica Israel but a spiritual kingom in heaven. Moral law was or was not abrogated (there is a controversy)