Big scary accounting term #2 --> LIABILITIES!
But really this is nothing to freak out over! Just think about these as items/money you are liable for - or owe to someone else.
This can be credit cards, loans, and sales tax you've collected but need to give to your state, gift cards, and bills when someone sends you an invoice that you haven't paid yet.
It's also important to keep this all separate in your bookkeeping so you can tell exactly how much you owe to whom <-- did I get that right grammar sticklers?