That... would take a little skill to explain without spoiling anything. The essential is that it's a tactics RPG where you command units where to move and who/how to attack (taking turns between your units and the enemy units). The story is about the Netherworld and the crazy things the demonic denizens get up to. And once you beat the story and go for post-game content, it's a numbers game on how to increase your stats in the most efficient way in order to defeat harder and harder enemies (where stats go into the millions with billions of HP).
I enjoy it and recommend it for anybody who doesn't mind a little bit of grinding. Also, be warned that it is one of those games that can be a massive time sink (like Civ V), as I've already clocked 150 hours in Disgaea 5 on PS4 and still going.
As for the PC release... it would be nice if they could package it with Disgaea Infinite and Disgaea D2: A Brighter Darkness in order to get all the stories relating to these characters.
EDIT: Also, mod support for this game would be awesome