Casual hang out: split the bill. Not really thinking about holding their hand or getting closer. Just having a good time like you're with your brother or sister. You know there could be nothing romantic between you.

Date: Could still split the cost, but you're thinking about what it would be like to kiss that other person. You're more concerned with learning about the other person than just talking about whatever. Your MO is to get to know the other person better rather than hang out. You're filtering through the conversation to see if you want to date them again. You have romantic feelings towards that other person.

I think if you're hanging out with someone you really want to date for too long, it will drive you crazy.