The full version of "Minecraft" is not available for free online. It is sold on Minecraft.net, but there is a demo version available for players who want to try out the game.
In order to download the demo that's available on the home page of Minecraft.net, players need to create a Mojang account, which is free to create. The demo allows players to try out the features and world of "Minecraft" before purchasing it. Many different versions of "Minecraft" are available, as it is a cross-platform game with versions on all devices and platforms, so players can check the app stores for their devices or game stores for demos as well.