Jesus is not on the cross because He rose from the dead. The cross is empty now. Catholics worship Mary, the mother of Jesus. Mary serves as an example of sexual purity and is prayed to because it is believed that Jesus will listen to his mother. Saints were so good on Earth that they went straight to Heaven.
Saints are active after death and can be prayed to.
The Catholic view of Heaven and Hell involves a middle ground called Purgatory. Saints were so holy they skipped Purgatory. Protestants don't believe in Purgatory. These are some of the major distinctives of Catholic Theology. There are many other differences in practice and teaching.