1%/10 Net 30

It's a fancy billing term. You bought something on credit. You get 1% off of the purchase price if you pay within 10 days otherwise the entire bill is due in 30 days. Thank you very much. Sort of like a discount in return for paying on time. So you think, "Wow, there must be a lot of deadbeats out there for this to actually be a Thing." And there are.