Spider-man Far From Home is based after the events of Avengers Endgame. (you must be living under a rock if you don’t know the outcome by now). Peter is mourning the loss of his mentor Tony Stark and is taking some time out to be a normal teenage boy, and is looking forward to a school trip to Europe and getting the chance to get to know MJ a little bit more.
This doesn’t go to plan when he finds Nick Fury in his Hotel room, in need of his help. Fury and Maria Hill introduce him to Quentin Beck aka Mysterio and Peter then has to decide between being an Avenger or being a teenager with a battle with the elements along the way.