Disclaimer: haven't yet seen this film.
Quentin Beck's story is fake, but obviously Marvel has an extensive multiverse which may (or conceivably may not) feature in future stories of the MCU. Quentin fakes the Elementals. He's a dodgy former Stark employee.
Nick is essentially on an exchange holiday in space. It seems to be a bit vague, according to viewer impressions so far, but Talos is standing in for Nick while Nick is supposed to be overseeing some obscure space-based project for Talos.
Since people aren't sure about the second post credit scene, here's the exact scene as it plays out.
Maria Hill and Nick Fury are driving in a car. Hill shapeshifts into Soren and Fury into Talos.
Soren: "You gotta tell him."
Talos: "It was fiiiiine. The little boy handled it. We helped..."
Soren: "Talos!"
Talos: "Come off it. How was I supposed to know the whole thing was fake? I mean that was all very very convincing, you know? The performances, the illusion, that costume; the craftsmanship in that. I mean it's just embarrassing for a shapeshifter. Fine."
Talos calls someone on the phone.
Talos: "Hey there I hope your mission is going well. We gave the glasses to Parker about a week ago like you said. And, uh that's very touching you know. Really, really quite touching. "
Soren: "Talos."
Talos: "And uh, you know, shortly after that everything kind of went off the rails and so we need you to come back. 'Cause everyone kept asking where the Avengers are and I don't know what to say to that so you're lucky..."
Fury hangs up the FaceTime and it looks like he's lounging on a beach. He's not, it's just a video wall in a little room on a giant Skrull ship. He gets up, he's in a t-shirt and barefoot, claps his hands and says "Everybody back to work" then walks to a huge open area where it looks like a space station or something in space is being built and says "Who's got my shoes?"
