Spirals are subdivided according to the prominence of the bulge and the arms:

  Sa -- large bulge, small arms, modest amounts of interstellar material and star formation

  Sb -- medium bulge, more interstellar material

  Sc -- small bulge, strong arms, lots of interstellar material and star formation

  Sd -- virtually no bulge

Here are edge-on examples from Sa (M104, left) through Sb (NGC 4565, middle) to Sc (NGC 891, right)

M104, an edge-on Sa galaxy NGC 4565, an edge-on Sb galaxy NGC 891, an edge-on Sc galaxy

And here are face-on examples:  (Sa: NGC 1302, GSC-II Image Gallery); (Sb: NGC 4826. Bill Keel); (Sc: NGC 628, Gemini Telescope)

NGC 1302, a face-on Sa galaxy NGC 4826, a face-on Sb galaxy NGC 628, a face-on Sc galaxy

Intermediate cases are given both designations -- like Sbc.

Color image of M33 Picture of an Scd-galaxy, M33, a member of the Local Group of galaxies and hence one of the closest to us (at about 800 thousand parsecs).
NGC 1365, a barred spiral galaxy NGC 3351, another barred galaxy
Also there is a barred (SB) series where the bulge looks like a bar. This picture is NGC 1365, a barred Sbc. This one is M95 = NGC 3351, a barred Sb spiral (hence with a more prominent nuclear region and less prominent arms compared with NGC 1365).