Payment terms in international trades are, you mentioned.
1- COD = Cash On Delivery, you can see this in some online purchase sites. which mean as the name implice. We dont need to pay to the supplier or seller at the time of Purchase. we can make payment at the time of goods received in hand. we can pay to this amount to our courier team, or the agent who make available this goods at your place. By this we can make more security for online or advance payment.
2- 90 Days - as name implies we can make payment to supplier after 90 days from the date of invoice. We can enjoy 90 days credit
3- 90 Days Da - DA means " Documents against Acceptance". as early mentioned we can make payment after 90 days from the date of Documents Accepted.