"Accounts receivable" is a technical term in accounting and finance. It means the money that a company is owed but has not collected yet. This happens when a company delivers some product or service and then collects payment later.
You can use this term to talk about the money that is owed to a company:
We have over $30,000 in accounts receivable.
If a company is large and has a lot of accounts receivable, they may have an "Accounts Receivable" department:
I work in Accounts Receivable.
This is a fairly technical phrase that English speakers who aren't accountants might not know.