What's an SLR?

I'm very good with a manual camera but know nothing about the digitals. Could some one tell me what an SLR is?

I thought it was single lens reflex. Somehow I was under the impression that it was something specific only to digital cameras.

no, it's nothing specific for digitals. for digital cameras it's "DSLR" - digital single lens reflex. a CCD sensor (the part that "captures" the image you're taking) replaces the film, otherwise they're largely the same.