survival and creative
There are 2 types of worlds: survival and creative. Survival is dangerous and creative is not. So, if your'e in survival STAY ALERT! If it is night, mobs will be coming! Build a house to stay safe! If you see a pig at night, 3 letters. RUN! Pigs transform into creepers! If you see anything else just run. For creative, there is no mobs unless you spawn them. So you can build whatever you want with no streas! You also have unlimited blocks unlike survival.