ARK: Survival Evolved is a game in a similar vein to other survival games such as Rust. You start off on a beach with nothing on you aside from an implant in your arm and have to survive from there.
Did I mention there's dinosaurs?
Yep. The game's got about 30 animals presently, with plans for up to 70. They're based off of extinct animals (not identical, which is lampshaded in game), ranging from the small, weak and stupid (dodos) to large, strong and still stupid (T-Rex) to the medium, fast and smart (raptors). Almost all the animals in game can be tamed, and many of those are large enough to be ridden with the appropriate saddle.
To start out, you need to make a pickaxe. It's one of the few things you can make at first. To unlock other recipes you need to level up, put a point into a certain attribute (such as water, food, health etc.), then use engram points you earn from levelling up to unlock engrams, which are the game's crafting recipes. These allow you to then start making weapons, other tools, houses and even fortresses.
The building can be split into two parts: houses and freestanding structures. Houses use a square foundation that can be linked with other foundations. These can then have walls, doors and windows put on them, then you can put a roof/ceiling on. Thatch roofs can't support a second floor, but once you get onto wood you'll be able to produce multi-story buildings, towers and so on, using either ramps or ladders to connect each floor. Freestanding structures are primarily used as walls/fences that you can use to make forts. You do this by getting a fence foundation and placing walls, windows and so on on top. The fences can be placed anywhere that's not too steep and do not need foundations to support them. This, in addition to the large gates you can make, make them perfectly suited to fortifying an area, making animal pens and funnelling animals/players into an area without much room to move. However, on PvP servers players are able to knock down these structures, and on both PvP and PvE servers, large dinosaurs are able to as well, so that gate you made will only be a stopgap measure against that T-Rex on the other side, and flying animals (and by extent, any people who ride them) can easily just fly over the top of the walls.
There's also a large cave system spread underneath the map, which contains tougher animals than usual, but provide access to metal. However, on PvE servers you will be unable to build in them because some players would block them off, and since on PvE you can't knock down player structures, nobody could get in.
And to help out along the way, there's a number of supply crates that drop from the sky or can be found in caves. The surface ones are marked by large beams in the sky, with different colours indicating the level required to open them. They can contain anything from random supplies such as stone, wood and thatch to foundations, walls and roofs to a full set of clothing/armour at the supply drop's level's tier. As a result, it's advisable you grab any that you come across that you can. Especially since after a few minutes from landing they'll decay.
There are also three monuments on the map, which on some servers will allow you to transfer player character info between servers. With the right materials, however, they can also do something else...
Find the trailer
here. The B12 server is Butosus, IP is 69.12.88.250:16166