Salvation is trusting in a work that has been done. Religion depends on our behaving. Salvation depends on our believing. Religion says we must act our best. Salvation says we must accept God's best.
Religion depends on the sufficiency of character.
Salvation depends on the Sacrifice of the Cross. Religion tries to furnish a sacrifice. Salvation trusts in a finished sacrifice. Religion is striving for a better attainment. Salvation is secured through a perfect atonement.