Student or Learner
whats the meaning of what in the world is this???
It's an emphatic way of asking "What is this?"
The person is surprised, shocked, horrified, very pleased, etc. There is some strong emotion connected with asking this way.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.