Empire, Den of Geek, and TrekMovie describe four clips of Star Trek in detail.  The clips are introduced with even more spoilers. After reading these three articles, you'll know about half the plot, including [ETA: maybe] the climax.

Even if you are a spoiler-phobe, I recommend reading about the first clip.  It isn't all that spoilery, but it's very WTF. There is a Budweiser product placement. In Star Trek. LOL.

Here is a small sampling of spoilers from all three articles:

Sulu and Uhura are cadets, but Kirk hasn't even entered the Academy yet.
Kirk is a Good Will Hunting-style genius. Sulu even calls him a "townie".
Kirk hits on Uhura in a bar. Says her knowledge of languages means she must have a "magic tongue". Sulu kicks his ass.
While getting his ass kicked, Kirk meets Captain Pike.
Pike makes Kirk try for The Academy.
Much later, shit happens and Spock leaves Kirk on a frozen planet. There he meets a time-travelling older Spock.
Scotty is also marooned on the planet for experimenting with transporters and killing "Admiral Archer's beagle".  OMG Porthos VII?
Old!Spock asks "you're Montgomery Scott?" as if he doesn't recognize this version of Scotty.

The spoilers make it pretty clear this is a canon reboot.  From what I've heard, there is an in-story explanation. Surprisingly, this has caused little gnashing on the Trek BBS.

Spoilers in comments, but only of the first three clips.  I think that is fair.