Meaning of the word "on earth" in English

What does "on earth" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

on earth

US /ɑːn ɜːrθ/
UK /ɒn ɜːθ/

Idiom

used for emphasis after a question or to express surprise or shock

Example:
What on earth are you doing?
How on earth did you manage to do that?