Hi Chip
A good textbook will give you a decent explanation of galvanic cells with a long list of applications etc. What aspects of them are you confused about?
I'll just give you a brief summary, see if I can steal a pic from somewhere as it's hard to understand without one...
CSU has a decent summary
here
"A galvanic cell is a device constructed so that a reductant and oxidant are physically separated, but connected by an external circuit made of a conductor (to carry electrons) and a salt bridge (to carry charged ions in solution). A galvanic cell is thus composed of two half-cells, a reductant half-cell and an oxidant half-cell. This arrangement ensures that electrons cannot go directly from the reductant to the oxidant, but they will move through the external circuit. "
See the page for the rest.