They were people that acted as dealers between two parties who wanted to exchange goods.

Could you please give me more information on this, no sites, just from top of your head, thanks very much:)

What does a stock broker, or real estate broker, or for that matter, a marriage broker do? Why?

A stock broker buys and sells shares, to earn money?

yes, so generalize: who are middlemen, and why?

The Middlemen were people that traded furs with a group to earn money...

yes, and exchanged the furs for goods the trappers wanted/needed. THe middlemen made money on both exchanges.

So they exchanged the goods two times?

Of course. they got furs from the trappers, they got food from river merchants, and the traded furs for food and supplies to the supplying merchants, and traded food and supplies for furs from the trappers.

The middlemen were in the middle.

The trappers brought furs to the middlemen and in return received goods they needed.

Then, the middlemen sold the furs to other people and received money.

Trappers >> Middlemen >> Consumer

Thanks so much, your explanations have helped me to understand so much better, thanks so much. :)

You're welcome.