What's a Remuda?

So here's a cool thing about horses.  The females rule!  (Stallions are for fighting, breeding, and protecting the herd - also important).  In a herd, the females decide where and when the herd moves.  And how about this?  They often lead together, shoulder to shoulder, in a line called a "Remuda".  Here's a cool photo of a Remuda that a friend of mine took a long time ago.