Heath is an inhabitant of Alexandria and is one of the community's supply runner. We see him regularly in Season 6 when he goes out of the community for supply with Glenn or Tara.
In the 12th episode of Season 6 Not tomorrow yet, Heath and Tara are on a long supply run when they are overwhelmed by walkers on a bridge. Their fate is unknown until Season 7 where we learn that Tara fell off the bridge and was rescued by the Ocean Side community.
Heath's fate is unclear. After leaving Ocean Side, Tara goes back to the bridge and Heath is nowhere to be seen. The character never appears in the series afterwards, though it would have been a useful asset in the war with the Saviors.
Out-of-universe, we know that Corey Hawkins, the actor portraying Heath, was chosen to be the protagonist of the short-lived 24: Legacy. But the show only lasted one season and he never returned.
The Walking Dead Wikia claims that Heath has been taken by the mysterious "Helicopter Group" that trades with Janus, without sourcing the claim by an episode title or a Word of God.
What happened to Heath in-universe?