He seals the believers unto the day of redemption. Salvation involves the redemption of the whole man. It is freely offered to all who will accept Jesus Christ as their Lord and Savior. He by His own blood obtained eternal redemption for the believer. In its broadest sense, salvation includes regeneration, sanctification, and glorification.
Baptism is the immersion of a believer in water.
It is the act of obedience symbolizing the believer's faith in the crucified, buried, and risen Savior, the believer's death to sin, the burial of the old life and the resurrection to walk in the newness of life. It does not save the believer but is the first act of obedience required of the believer. The Lord's Supper is a symbolic act of memorializing the death of Christ. His body was broken for us and His blood was poured out as the new covenent. We are to do this until He returns.