Blip

"You remember everyone Thanos snapped away five years ago and just bringing them back to now, today... Don't change anything from the last five years."

- Iron Man to Hulk

The Blip was the occurrence in which Bruce Banner wore Tony Stark's Nano Gauntlet. As Hulk snapped his fingers, the effects of Thanos' Snap on the universe was reversed, with the deceased half of its population being resurrected five years after their demise.

Background
"All right, the glove's ready. Question is: who's gonna snap their frickin' fingers?"

- Rocket Raccoon

As all of the Infinity Stones are gathered back into the present, the Avengers realized Black Widow sacrifice to gain the Soul Stone. Determined to not let Natasha’s sacrifice be in vain Tony Stark, Rocket Raccoon, and Bruce Banner began working on a new Infinity Gauntlet. After the creation of the Gauntlet was complete, Rocket asked who was going to be the one to reverse the Snap.

Reversal
"You saw what those stones did to Thanos, they almost killed him. None of you could survive." "How do we know you will?" "You don't. But the radiation's mostly gamma. It's like I was made for this."

- Hulk and Captain America

At the moment when the Nano Gauntlet was set for completion, Thor volunteered himself to put it on, but the Avengers held him back, saying he was neither physically nor emotionally stable enough to do so. Bruce Banner volunteered himself, reasoning that as the Stones and his body contained mostly gamma radiation, he was the most likely to survive the use of the Gauntlet.

While Stark ordered F.R.I.D.A.Y. to initiate lockdown procedures across the facility in case the Gauntlet's energies proved to be too powerful to contain, an alternate Nebula began to sabotage the quantum device as Banner put on the Gauntlet. The Avengers began worrying for him as Banner channeled the power of the Stones through his body, severely scorching his arm in the process. The Sanctuary II emerged and crashed through the roof of the facility, destroying the quantum device, just before Banner snapped his fingers, bringing everyone who Thanos snapped back.

Battle of Earth
"Doctor Strange was there, right, and he was like "It's been five years, come on, they need us." And then he started doing that yellow sparkly thing he does all the time."

- Spider-Man to Iron Man

Ant-Man guessed that the mission of resurrecting the universal population worked as he looked outside at a group of birds that appeared out of nowhere, while at the same time Hawkeye received a call from his wife, who had previously perished in the Snap. As the group started to realize whether or not their mission had been completed, a dazed Bruce Banner noticed Thanos' mothership from above the window ceiling.

Before he could react, Sanctuary II fired upon New Avengers Facility, destroying it and causing the Avengers to be separated from each other, although Hawkeye is able to take possession from the Gauntlet. The effects of the Blip become apparent during the ensuing battle when Captain America received a transmission from Falcon, one of the victims of the Snap, and the rest of the resurrected started appearing shortly thereafter through portals created by Doctor Strange and other sorcerers.