It is exactly what it says it is, interest free credit.
When a company buys something from a supplier they typically will not pay for it immediately. They will be given an invoice and it will have terms that look like " 2/7 n/30". This means that you can recieve a 2% discount if the bill is paid within 7 days, or the payment of the bill in full is due in 30 days.
It provides a very short term financing arrangement for the purchaser because instead of having to pay cash upfront they can use that cash elsewhere for 30 days at no cost. Of course, there is an opportunity cost involved if the purchaser wants to wait the whole 30 days before paying bill, that is the 2% discount.
Note: my first post was garbage because something is going on with my internet. My internet is really slow and it will only the the first post in the thread :|. I cannot see any other posts in the threads until my download limit resets in 2 days :|