There are a variety of types of trains.
The basic progressive 'train' starts with one trader who puts an amount of coupons, ie., 25 and sends it to the next 'rider'.
That second rider would take out the coupons that he/she can use, along with those that are near expiration; add additional coupons to meet the train rules, ie., 25, then forward the envelope to the next 'rider' on the train.
On other trains, traders are matched up to mail out one envelope to another trader; so that each trader would mail out one, and receive one envelope.
There are lots and lots of twists and turns (criteria) a train conductor can make,
so be sure to read all of the rules for each train you are interested in
before signing up!
Best of luck!
Trains are a great way to acquire a variety of coupons - hopefully, some that match to your wishlist!!