Good Friday is observed as the solemn day of Christ's crucifixion. The reason it is called Good Friday is because Jesus died for us and because of his death, we are saved from death and sin. This day is celebrated in a spirit of thanksgiving for the marvelous gift that Jesus gave to us.
Before Jesus came and died for us, priests would offer sacrifices to God in order to have the sins of the people forgiven and to reconcile them once again with God. In His ultimate wisdom, God had set up this system which would eventually point to the ultimate sacrifice that Jesus would come to make for the good of all humanity. Therefore, the early Christians were looking ahead to the Cross, as we today, look back to the Cross.
The system that God set up was a system where high priests would offer sacrifices at the temple. Blood was shed and the priest would pray for the forgiveness of the people. The blood from these animals that was shed would point to Jesus' blood who would forever wash our sins away. Christ, our Paschal Lamb, was sacrificed in fulfillment of what had long been promised and prophesied in the Bible. The true Lamb replaced all other symbolic lambs, therefore many offerings of the past gave way to the single sacrifice of Christ.
When Jesus died for us, he became both our great high priest and the one and only sacrifice for the forgiveness of our sins.
From noon onward,
whole land ...
cried out again
in a loud voice,
up his spirit.
Matthew 27: 45-50