Path of Exile is a game by Grinding Gear Games. This game is an Action RPG, an ever expanding and popular genre. It has many similar qualities of other popular RPGs such as Torchlight 2 and Diablo three, having a very similar HUD. What you see in many RPGs is little differentiation from each other. While all of them are different, there is often a strong reminiscence of some other RPG, which isn't at all a bad thing, but sometimes it's a nice change.
What Path of Exile does it brings to the table the 'Skill Gem System.' In this game you have skills from gems you find but, there are also support gems which augment your skills with gems you find from different things. These gems can be 'socketed' into an item you possess and that's how they are activated and used. These skill gems can make it so you shoot a fire ball that chains from enemy to enemy, or shoots out five fire balls instead of one or will amplify the AOE of that attack. This can lead to hundreds to even thousands of different combinations of skills.
This game, as most RPGs do, has a class system in it. These classes are Duelist, Witch, Ranger, Shadow, Templar and Marauder.
(Classes in order from left to right: Duelist, Witch, Ranger, Templar, Marauder, Shadow.)
Each class focuses on one or two of three attributes: Strength, Dexterity or Intelligence.
Strength: Classes under this attribute focus on using high damage weapons and heavy armor, your generic beat down warrior kind of character. Classes under this attribute: Marauder, Duelist, Templar.
Dexterity: Classes under this attribute use light, fast hitting weapons and armor that promotes evasion, your generic rogue or ranged kind of character. Classes under this attribute: Ranger, Duelist, Shadow.
Intelligence: Classes under this attribute tend to be smarter quick finishers, using magic and aiming for critical hits instead of beating enemies senseless and your armors tend to be of magically inclined that recharge outside of battle; your generic assassin or obviously wizard. Classes under this attribute: Witch, Templar, Shadow.
Creatures and items will also be under one of these attributes: for example a staff is usually 70% strength, 30% intelligence as it has a greater chance to get critical hits at the cost of losing just base damage. Characters are able to use other weapons that aren't part of their attributes by investing in the other attribute(s) but it's generally going to be better just to invest in your classes attributes.
Passive Skill Tree
In Path of Exile there is one massive skill tree (contains 1350 skills) which all classes share, but start in separate places based on what they are. You can get any passive skill which any character, but some skills will take longer to get to with the marauder than with the shadow. Some examples of what these abilities is that they can make it so your attacks will always hit home, but at the trade off of never getting a critical hit. Another example is an ability that grants the abilities of your shield to your minions instead of you. (I'm like eighty-five percent sure that's meant for witch as I don't know if any other character can summon minions.) You gain a skill point for this skill tree at every level.
An overview of the skill tree.
(Sorry couldn't get a bigger picture, but all the little white dots and lines are the skills and paths.)
The World, "Wraeclast"
The world in Path of Exile is, as described by Grinding Gears Games, "Wraeclast is a dark, brutal continent. Scarred by mysterious catastrophes of the past and inhabited by creatures of nightmare, the very environment challenges exiles who dare explore it. We're sick of the recent trend towards bright, cartoony RPGs. The art style we chose for Path of Exile is dark, gritty and realistic. Wraeclast is terrifying, and we've tried hard to do it justice."
What Grinding Gears Games wanted to do was to make it so you wanted to play again and to do this they've made it so that the world is randomly generated when you play, so the loot and monsters will be different almost every time you play.
(The beta video of Path of Exile)
This game has more to it then what I've mentioned here, but I've summed up a large chunk of this game. This game is currently in closed beta, but on the twenty-third will officially be in open beta. The game is going to be a free to play game, where you can buy items (purely visual items as GGG says they hate Pay 2 Win games and for good reason.) in order to support the game. You can buy this game for ten dollars in closed beta with one hundred coins. You are able to donate more to gain more but gaining a few more things. (Including being in the credits for the game, free T-shirts, acknowledgement as supporter on forums and an item of your design and a bunch of other stuff (all that's stuff is for paying $1000 though)) The game doesn't have an official release date but is set for 2013.
(Note I haven't played this as of yet, this is from research (I have time on my hands don't judge me!) but I'm looking forward to it and will most likely post a review of it)