Major Avengers: Endgame spoilers ahead. As everyone knows by now, at the end of Avengers: Infinity War, Thanos snapped his gauntlet covered fingers and killed half of all the living creatures in the universe. And as everyone also knows, there was no way they would all stay dead, because there are many more superhero movies to be made. (Plus, that would be a huge bummer.) But now, with the release of Avengers: Endgame, we know what ended up happening, along with details like where everyone went during the Infinity War snap.
As we saw in Infinity War, the people who were killed simply turned into dust, but what did that really mean for them? Were they at all conscious of what happened? Did they go to an afterlife? Is Peter Parker in The Good Place?
Well, by the end of Endgame, we get our answers, and they're delivered by the resuscitated Spider-Man himself. In a couple lines of exposition, Spider-Man tells Tony Stark that after he turned "all dusty", it was like nothing happened and the next thing he knew Doctor Strange showed up and brought him back to Earth for the big Thanos battle, take two.
So, in the minds of Spider-Man and all the other Avengers who were killed, they went from dying in an attempt to stop Thanos to being found by Doctor Strange and immediately going back to battle Thanos again. Talk about a stressful day!
A stressful day that was really five years long for everyone else, that is. Because that's how much time had passed for the living half of the population. There is a five-year time jump toward the beginning of Endgame that follows another failed attempt to retrieve the Infinity Stones. It took five years for another viable plan to come up, this time via Scott Lang/Ant-Man, who had been in the Quantum Realm for those five years and presumed dead like so many others. As some fans guessed, the Avengers do go into the Quantum Realm and use it to time travel to try and stop Thanos' snap.
While, of course, it was sad to see the Avengers watch their fellow Avengers disappear at the end of Infinity War, Endgame shows how that snap affected other, regular humans, too. There are big monuments put up in honor of "The Vanished," signs posted for people who still may be missing, but not dead, and support groups (including one led by Captain America) for those who are mourning their loved ones. The film also opens with a particularly chilling scene in which Clint Barton/Hawkeye witnesses his own family's disappearance.
By the end of the movie, all of the normal, non-Avengers population is restored, too, so based on what Spider-Man said, they must have just woken up with the last thing they remember being that they felt kind of weird. And perhaps they're five years younger than the people who didn't disappear. But what about the ones who died not from turning to dust, but from the effects of other people being snapped (for instance, the many, many car crashes that surely happened)? Do they get to return?
However that very dark scenario checks out, the point is, the people who left because of the snap are back. Also, anyone who is licensed as a therapist will be in very high demand.