I know that this is more of a general photography question rather than an aviation photography question, but I was hoping someone could answer this question for me. What exactly is a rangefinder camera, and how does it differ from a regular SLR camera? I've seen this type of camera offered for sale at sites like Adorama and B&H, but the product descriptions never really explain what "rangefinder" means. Aside from just about all of them being manual focus and very expensive, there's nothing else that indicates what makes it different than a regular SLR.
I'm not thinking about getting one or anything (not at those prices!), just curious.