“Now what exactly are account receivables?”
You're chatting with someone at a party who you haven't spoken with very much. He's telling you about his job, but he works on something that you don't know much about. You ask for an explanation.
Now what exactly are account receivables?
You can introduce a question with "Now..." to show that you're a little confused about something:
Now what was your name again?
Now when did that change? I thought it was supposed to be on June 23rd.
Ask "What exactly...?" when you want someone to answer your question with a lot of detail. For example, you can ask this question if you know that someone works in a factory:
What exactly do you do at the factory?
You can ask this if your child is upset about something but you're not sure why:
What exactly is the problem?
"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.