It's a general trailer for the series as a whole, so it doesn't give any specific story detail. However, if you scroll down, you'll find a blurb for the first story in the series, GUARDIAN.
1. Receive assignment.
2. Save a life.
Protecting humans from dangerous magical creatures is all in a day’s work for a faerie training to be a guardian. Seventeen-year-old Violet Fairdale knows this better than anyone—she’s about to become the best guardian the Guild has seen in years. That is, until one of her assignments—a human boy who shouldn’t even be able to see her—follows her into the fae realm. Now she’s broken Guild Law, a crime that could lead to her expulsion.
The last thing Vi wants to do is spend any more time with the boy who got her into this mess, but the Guild requires that she return Nate to his home and make him forget everything he’s discovered of the fae realm. Easy, right? But Nate and Vi are about to land themselves in even bigger trouble—and it’ll take all Vi’s training to get them out alive.