Here's a breakdown:
* Hallo: This is the German word for "hello."
* was: This is the German word for "what."
* ist: This is the German word for "is."
* los: This word is a bit tricky, as it doesn't directly translate to "up." It means "loose" or "going on," but in this context, it's used to ask about what's happening or what's new.
So, the whole phrase "Hallo, was ist los?" is a casual and friendly way to greet someone and ask them what's new.