Since noone has actually answered your question, it's essentially a giant ass sandbox. It spawns randomly generated worlds in which you spawn with absolutely nothing, and work your way up from cutting down trees to mining deep underground for diamond or exploring huge cave systems. To spice things up, zombies that are dead siilent and explode upon touching you and skeleton archers roll around in the dark, underground and during the night. Everything you make is made my combining things you gather. It's also really, really addicting.