Minecraft is a sandbox construction game. It is like a giant world of “virtual legos”. It can be played in four different modes. Classic, Survival, Hardcore and Multiplayer.
You have all the materials, but the world is not as big as in Survival and Hardcore mode. You have endless blocks, so it’s a good way to start and try out the game.
You start out with nothing. You have to gather resources by for example cutting trees, mining resources etc. With the resources you will find, you can craft various of different blocks, items, weapons etc. Check out all the crafting recipes.
It’s a good idea to start out by making a house, shelter or somewhere to hide when it gets dark. This is why it is called Survival mode, when the darkness arrives, different types of monsters appears too. The monsters doesn’t like light, therefore you need to make some tourches and build a nice house for yourself in order to survive.
Same as Survival mode, with one exception: when you die, you have to start all over. When you die in Survival mode you only loose the stuff you have in your inventory and respawn the place you started. Hardcore mode is also locked on the hardest difficulty.
The most common modes in multiplayer is Classic or Survival. Some games are called Free build, here you are in some kind of classic mode, but with no terrain so you can just build. Some games haves different mods installed, making the modes almost endless.