“What's the deal with this soup?”

You come home and your wife is watching TV. You see that there's a pot of cold soup on the stove, but you don't know whether it's good to eat or whether it needs to be thrown out. You ask:

What's the deal with this soup?

What's the deal with (something)?

This is a question that you can ask to get general information about something. "What's the deal with ___?" isn't a specific question, so the person who you ask can give whatever answer is appropriate. In the situation above, the wife can give any of these answers:

Oops, I made that for lunch but I forgot to put it away.

It's an Italian recipe I came across the other day.

It's still good. Just heat it up a bit.

Ask "what's the deal with ___" for things that are a little strange or unexpected, when you want to find out information about them but you don't know what exactly to ask.