In the most basic terms, Northgard is a viking themed real-time strategy game from the makers of Evoland. It belongs somewhere between the Civilization and Settlers series as it features many of the same gameplay ideas, though currently its far simpler than both.
If you're wondering what all of this might look like in gameplay terms, you'll find the official launch trailer down below. Additionally, if you want a lengthy preview showcasing the first 15 minutes of a match, you'll find my gameplay showcase video right here. But for now, here's the much more succinct trailer:
As for whether Northgard is worth your money or not, that is a bit of a tricky question. On one hand I must admit I had a great deal of fun with it so far, but I also have to say that its currently both unfinished and far too easy. If you're interested in all of the reasons why you'll find my detailed opinion in the preview/review, but long story short, unless you're a fan of RTS games I would recommend waiting a month or two in order for the singleplayer campaign to arrive.