After the shocking events of Avengers: Infinity War (2018), the universe is literally split in 2. With the assistance of the remaining team members, the Avengers assemble once again in order to try and reverse Thanos' actions and regain balance in the universe.
Directors of 'Avengers: Endgame'
"You have to have a very cohesive plan. You’re making thousands of decisions a day. There are multiple filming units, there’s a whole visual-effects team, we have actors coming to us, saying, “I wouldn’t say it this way, I’d say it that way.” Our job is to collect all this information and be the arbiters of taste and provide focus for the entire process. You have to leave room for everyone else to be empowered and assist in making creative decisions."
Currently you can only stream Avengers: Endgame through Disney+, the streaming service from Disney. So you'll need a subscription to Disney+ to access the film online - you can use a 7 day free trial if you want to try out the service before subscribing. If you're streaming the movie through Disney+, you'll have to pay the monthly cost of Disney+, which is $7 per month in the United States.
If you don't have Disney+ and you don't want to sign up to the platform then you can buy or rent Avengers: Endgame to watch online through Amazon Prime Video, iTunes, FandangoNOW, Microsoft Store, VUDU or Google Play Movies. You can rent the movie for as little as $3.99 or buy it for as little as $9.99.