"Folk and blues" denotes musics that overlap at points but ultimately part ways. Early down-home blues was a style of tradition-based music shaped pretty much in the way folk songs were created and passed on. By mid-century (or a little earlier) blues as a popular genre began to create its own story through a range of broadly comparable styles, some far removed from the original rural variety that one can reasonably link to folk.

Guys like Howlin' Wolf, Muddy Waters, Johnny Shines, Big Walter et al. are folk musicians of a kind, in my opinion. I wouldn't apply that characterization to more uptown, jazz-influenced artists such as BB King, Little Milton Campbell, Bobby Bland, T Bone Walker, Charles Brown, and the like. I love all that stuff, but today most advertised blues is the work of flashy white rock guitarists in search of faux-authenticity. As a regular CD reviewer I hear enough of this to wonder if blues has a future.

For some recent examples of blues as folk, there's Taj Mahal & Ry Cooder's "Get on Board" (Nonesuch) and Charlie Musselwhite's "Mississippi Son" (Alligator) -- both well worth your attention if this kind of approach interests you.