Decided to ask here since it did not appear appropriate to post in coupon connection or any other place. Please move if needed.

I have read the coupon connection for years and I still have a big question. How do people trade miles? I thought it was a "I'll book a ticket for you with my miles" and "you book a ticket for me with your miles". However, that is complex plus I see a lot of posts wiht odd number miles.

Do they use points.com? That has a huge devaluation of miles so it can not be that.

How does an efficient trade work?