twinrambull
Many of the cards have meanings that can overlap a bit. But I feel the general thrust of the Rider is that something/someone is coming, while the Letter represents written text.
Okay, so now that brings me to another question....the difference between Rider and Stork? I see similarities in both their meanings now that you said Rider could indicate an incoming, generally speaking.
Lenormand is so much more confusing than I though