Physical death.

Before Adam’s fall he had the potential to die physically, but not the necessity to die physically, this can be deduced from Gods provision for eating in Genesis 2:16-17 “The LORD God commanded the man, saying, "From any tree of the garden you may eat freely; but from the tree of the knowledge of good and evil you shall not eat, for in the day that you eat from it you will surely die.” (Emphasis added)
After the fall physical death became a necessity for everyone, (Hebrews 9:27 “And inasmuch as it is appointed for men to die once and after this comes judgment”) except those believers who are caught up to be with the Lord at the time of the rapture. (1Theselonians 4:16-17 For the Lord Himself will descend from heaven with a shout, with the voice of the archangel and with the trumpet of God, and the dead in Christ will rise first. Then we who are alive and remain will be caught up together with them in the clouds to meet the Lord in the air, and so we shall always be with the Lord.)