Ok, ive bought it, now what do it do !
I'll admit, it looks like fun but I am so confused atm.
Ok, assuming your playing single player. First of all it'll be day, but night is coming and with night.... comes monsters!
First of all get some wood, find a tree and bash away at the trunk. It'll disappear and a wood block will fall. Pick it up and you'll be holding a wooden block. Use it to bash more wood until you've got about 13-14 bits of wood.
Next find a cave with some coal, stone with black flecks through it. If you press I, it'll take you to an Inventory with a small crafting section of 4 empty spaces you can place stuff in. Drag all the tree trunk blocks in here and a picture of wooden planks will appear on the right. Keep clicking that until all the tree trunks are gone. Now you have planks, but what will I do with planks I hear you say?
Now you make sticks, do this by dragging the wooden planks into the crafting box in in the Inventory screen (I). This time, put half the planks on one sqaure in the bottom and half in the top. Now pictures of a stick will be on the right. Keep clicking until you have lots of sticks but don't use all your planks!!
Put 1 plank in each of the 4 crafting spaces and a crafting block will appear on the right. Take this and drop it in the cave near the coal by right clicking in front of you when your holding it. It'll appear on the ground. Now right click it and you'll have a crafting screen with more spaces. Take the sticks and put them in the bottom middle and lower middle middle of the crafting screen. Then take 3 planks and place them along the top of the crafting screen. Like this (= means Sticks and @ means planks and ... is empty)
@@@
...=...
...=...
This will make a pickaxe which you can use to mine, mine some stone and some coal and then make a stone pickaxe which will last longer. This is done in the same way as above but substitute planks for stone blocks. Once you have coal you can make torches for light, this is done by placing one stick and one bit of coal with the coal on top of the stick in the crafting box. Now you can make light.
Now your fully armed to enter the world of Minecraft, try and block up your cave with stone or mud or anything so your safe for the first night.
Reading the minecraft wiki is a good idea too
http://www.minecraftwiki.net/wiki/Main_Page