You can't steal things from people's inventories.
However if someone drops an object, puts it in a chest, nothing stops you from taking it.
Many multiplayer servers though will have a way of making things private, ie, only allowing certain people to open certain chests. That way someone can have a private chest that only they can access.
Chat with our AI personalities
Yes, but they will find out and delete your account.
It is called Minecraft because you mine stuff and craft stuff.
you must go to the aether by getting the aether mod mine some purple stuff and craft it like you craft a sword
There is only one way to do this. In game there is a gear item called the bucket. This item allows you to swap out your bucket for a players gear item they are currently holding. Other than this there is no way to steal a player's items.
You need to level up to enchant items.