When you include terms on an invoice, the terms remind your customer when the payment is due. The name you give the terms actually appears on the printed or delivered invoice if you customize the invoice to include the Terms field.
Terms on a bill remind you when the bill is due to be paid to the vendor.
To add new terms:
Tip: You can give a customer or vendor default terms. To give a particular customer or vendor terms that will be assigned to invoices or bills by default:
The next invoice you create for that customer or the next bill you enter for that vendor uses the terms you assigned.