The new series will carry on from the scene in Avengers: Endgame when ANT-MAN and Tony Stark travelled back in time to recover the Teseract from his former self.
After ANT-MAN creates a distraction Tony grabs the Teseract but as HULK smashes through the door he drops it and it falls in front of Loki's feet. The new trailer shows us what happens after Loki escapes. We see him taken to the TVA aka Team Variance Authority which is an organisation which police the multiverse. The new series will follow Loki through time and multiverse with no question that he will be creating mischief on the way, what else could you expect from the God of Mischief!
This, out of the three new Disney+ series's, is the one I am most excited for. After first seeing him in THOR way back in 2011, myself and many fans, loved Tom Hiddleston's take on the mischievous Loki. He set the standards for Marvel's villains and I don't think any have been as popular since. I am very excited to see him return with the first episode being released on June 11th 2021.