Meaning trap
go on
happen
To take place or occur, especially when something is surprising or unknown.

Don't mix these meanings
Same phrase, different job.
To take place or occur, especially when something is surprising or unknown.
Another meaning of 'go on' is 'continue'; compare the examples to keep the meanings separate.
Hear it in context
Notice where the phrase sounds natural.
There was a lot of noise outside, and I wondered what was going on.
When I arrived at the meeting, I didn't understand what was going on at first because everyone was talking at once.
Fix the pattern
One small grammar move makes it sound right.
Not: What's going here?
Say: What's going on here?
In this sense the particle 'on' is required — 'go on' means happen; 'go' alone doesn't.
Which sounds natural?
Tap the one a native speaker would say.
'What's going on?' is the natural way to ask what's happening. 'What is occurring' sounds like a police report.
Build natural chunks
Words that usually travel with it.
go on
- what's
- something
- a lot
- what on earth
Don't confuse it
Related
Other meanings and phrases to compare.
- go on (continue) — Another meaning of 'go on' is 'continue'; compare the examples to keep the meanings separate.