What is the main idea of Minecraft?

Minecraft is basically for doing what you want, building what you want etc. It's really for creative people so if you are creative you should try it
It'd be a 8/10 from me because of all of the mods downloadable

Basically it's like 3D legos in a pc game
it's like no other genre out there

creative mode: you needs to have a project (probably needs creative thinking), in this mode you have infinite materials and free flying to build stuff like malls, airports, hotels, towers, tomes, temples, anything you can think of can be made in the game and i mean anything… You can play monoplay in minecraft but that's an adventure map (i'll explain that).

survival mode: you have a health bar, hunger bar and you have to eat from time to time… If you wanna build stuff you need to go take down a tree to get wood, you need to make an pickaxe to get stone and make better tools… So you can keep mining to get even better materials until you get the precious diamond.
for me survival mode gives u a challenge and you feel like you really accomplished something when build something big… Plus you get to fight monsters and go to different worlds other than the normal world.until getting to the END where you get to fight the final boss.

adventure mode: you can download maps made by other people… These could be puzzles, mysteries and other fun stuff depending on who made it. You would be really amazed at what people have made.

multiplayer minecraft is the best part though. You get tojoin communities and build whole towns and cities with everyone having their own role… Or you could join a pvp server and just fight other players.

all in all i totally recommend it… Check out some youtube videos if your still not convinced 10/10
ps. Spleef is awesome