The King of Fighters XIV is a 2D fighting game, which uses 3D models. It features 50 playable characters and a very deep combat system.
Pro Deep gameplay
KoF 14 is simple on the surface: pick a character, learn some special moves, a few combos, and go to town on your opponents. However, if you want true mastery of the game, it's going to take a lot of time and effort.
You'll have to learn things like cancels, where you stop a combo with a specific input on your controller, in order to continue in a different way than the game intends. Fighting games are often about who can break the game's engine the best, and KoF 14 is no exception.
On top of things like engine breaking, you'll also have to dedicate a large amount of time to learning your chosen character(s) in order to be truly great with them. Every character has complex combos that require precision timing and great reaction speed, and you'll have to get all of them down.
The fact that you can play this casually with a friend and just mess around for while, or practice as hard as you can and truly try to master the game really makes it fun.