How do you say what happened in Portuguese?

There are a few ways to say "what happened" in Portuguese, depending on the context and formality:

Formal:

* O que aconteceu? (What happened?)

* O que se passou? (What happened?)

Informal:

* O que foi? (What was it?)

* O que rolou? (What went down?) - This is more slang and means something like "what happened, what went on"

* O que houve? (What happened?) - More common in European Portuguese

In addition to these, you can also use:

* Pode me explicar o que aconteceu? (Can you explain what happened?)

* Diga-me o que aconteceu. (Tell me what happened.)

The best option will depend on the situation and your relationship with the person you are talking to.