There are lots of things to do in minecraft, you can choose to survive,or have infinite resources.
You have infinite resources, can't die, you can fly into the air, and one hit blocks.
You don't have infinite resources, you can die, you don't one-hit blocks, and mobs can and will attack you. You can't fly.
You can't break blocks, can't place blocks, you can use tools, and you don't have infinite resources. It is almost impossible to beat this mode you need to be very, very, very, very, lucky to beat it.
You have 1 life, and it is stuck on hard mode. It is very hard.
There are very little hostie mobs, and they do less damage. You lose less hungry.
There are no hostile mobs, and you lose no hungry.