It literally means WHAT THE FUCK
Jonn Wtf are you doing bro?
Chad I’m doing your mom
Jonn WTF!?
1. used to exclaim emotion in a sentence, usually anger
2. the abbreviation of 'what the fuck'
1. wtf why did you just steal my fucking phone?
2. wtf do you mean
used as a reply on something funny,sad,weird,scary or that makes you unconfortable
ex1
twitter user1: Age of consent should be lower
twitter user2: WTF?
ex2
boi1: my dog died yesterday
boi2: wtf man im sorry