What happened vs. What's happened

[MadHorse]

Are they both correct?
'What's' is the contraction of 'what is', not 'what has', right?
Thanks.

[rewboss]

Here, "what's" is the contraction of "what has". This is the present perfect, which is constructed using:

1. the helping verb "have"
2. the past participle of the main verb

The meaning is almost the same, but not quite. You would use "What happened?" to refer to an event in the past; "What's happened?" refers to an event in the recent past which has an effect on the present.

For example:

"I was expelled from school in 1998."
"Why? What happened?"

(Peter drops a tray of cups and saucers. Mary hears the noise from another room)
Mary: "What's happened?"

[qwertyuiop]

"What's" can either mean "what is" or "what has" (but contractions are informal, so they shouldn't be used in formal documents). In this case "What's happened" means "What has happened", not "what is happened". "What is happened" is incorrect.

[qwertyuiop]

Sorry, haven't noticed someone has answered that.