What's new is a casual request for somebody's recent news. Hello, stranger, what's new.
It opens a conversation rather than asking a real question, and nothing is the standard answer. Said with a shrug about something familiar it means the opposite, that nothing ever changes.
1phrasewhat's newA casual request for somebody's recent news.
“He sat down with his coffee and asked what's new.”
what's new is a question.
Practised in Small Talk & Everyday Phrases