People of all ages can play Minecraft. However, children under the age of 13 are unable to create a Mojang account without their parents permission.
By default, if you are playing a demo version of Minecraft your email address will be displayed instead of a username. If you are playing with a paid version of Minecraft, your username, age and country location can be seen by other players in the game.
If you do not want to share any information with other players, you may choose to create and/or play on a private server. This is called whitelisting.
Minecraft are unable to moderate player behaviour or server content. All servers are privately run, and players are responsible for their actions server to server.
If you are having trouble on your server, Minecraft suggest researching anti-griefing mods, and whitelisting your server so that only selected people can access the game. If you are having trouble on someone else's server, please contact that server's administrator or moderator team for assistance.
Right: an example of Minecraft's Support Centre.
Minecraft can be played for free by downloading the demo version of the game.
For a fee, you can purchase a paid Minecraft account that allows you to download the full version of the game. Minecraft also has an online store where game related merchandise can be purchased. If you make a purchase through the online store, you will be asked to provide billing information including credit card details.
Right: an example of Minecraft's Store.