Basically, it is the trope of a group of kids rising up to fight the "great evil", while going to school. Not unlike Harry Potter in that sense, but RWBY is set in its own universe, and every character has their own unique power and weapon, which. in my opinion, is admittedly pretty much the only interesting thing about it at first.
The main character, Ruby (it'll make sense later), is a fifteen year old girl whose weapon is a scythe that is also a sniper rifle. Another character has twin blades that combine into a bow. The jist is that virtually every character's weapon can transform into a gun.
Another comparison that can be made to Harry Potter is the fact that it is Rooster Teeth's intention to make the characters, and indeed the series, evolve and age over time. In the first volume, the characters are fighting against some bad guys while getting to know one another. By the end of the third volume, they are dealing with the fracture of society as they know it. But at the same time it doesn't feel as though it escalates too suddenly. It is easy to follow and a lot of fun. I hearken it to Pacific Rim (the most readily available example in my mind). A lot of the fighting in that movie was absurd and unrealistic. Remember when Gypsy Danger used a tanker as a bat?
But when you're watching it, you simply don't care that it's completely unrealistic. You're just excited to see that it's happening. It's the same thing with RWBY. Ruby uses her sniper to give her momentum in battle, but if the gun had that much kickback then it would be much harder to use, to say the least. And coming from somebody who is very critical of things and sometimes has trouble suspending disbelief, I don't care. It's awesome.
So the disclaimer I'll give is that RWBY has a bumpy start. The only thing I enjoyed about the first few episodes was the prospect of seeing other characters' weapons. The dialogue is clunky (though hilarious at times), the plot is nothing special, and the animation can be hard to enjoy. But the show somehow helps fill a void in my creative soul. So, if any of this does sound interesting, I would recommend it. Watch the first eight episodes (Players and Pieces is Ep. 8). If you aren't interested in watching the next episode after that one, you probably won't like the series. That equates to just under an hour, because the first several episodes are pretty short.
As of yet, the third volume just finished (as of February, 2016). At first, I was only interested in the fighting, but now I actually care about the characters as much, if not more. I have no clue how long it will be before the next volume, but I suspect they're already hard at work.
If you read the forums, the wikis, the facebook pages on RWBY, you will see how much love was put into this show. If I remember correctly, the original creator, Monty Oum, had planned out eight volumes. With as good as volume three was, I'm pretty sure the hype train has already left the station. And as well all know...
RIP Monty. To a creative soul, and a great man!