Here is something I think I get but just want to verify. I am building a bar and want to have an outlet as well as a switch that controls a light for the counter under the bar top. I was thinking of tapping into the existing wiring that controls a couple of outlets in the room. I wanted to go from that, into the GFI, then into the switch and finally into the light. So anything downstream of the outlet would go cold if anything in the bar area got wet (I also am having a sink). Is this correct?

If you wire your GFI per the instructions in the package, everything "downstream" will be protected.