Death vs. Eternal life

Through one man, Adam, sin entered the world,

and death came through sin (Rom. 5:12).

The wages of sin is death (6:23).

Here, "death" refers to:

1. Spiritual death, separation from God.
2. Physical death, the separation of body and soul.
3. Eternal death, being completely separated from God and facing eternal damnation.

However, through one man, Jesus Christ,

we have been justified and received the gift of eternal life (v. 18, 6:23).

The gift of God is eternal life in Christ Jesus our Lord (6:23).

Here, "eternal life" means:

1. Being connected to God through Jesus Christ.
2. Knowing the one true God and Jesus Christ (Jn. 17:3).
3. At the Lord's return, experiencing a transformation of the body (if still alive)

or resurrection (if deceased), being united with the soul,

and entering the new heaven and new earth,

which is the eternal kingdom, to dwell with God forever.