When a provider advertises she is located in the Gold Coast area, what does that mean? It is a large area where Chicago borders Lake Michigan. Is it the downtown area near the lake?

http://en.wikipedia.org/wiki/Gold_Coast,_Chicago

http://www.chicagotraveler.com/neighborhoods/gold-coast-neighborhood-map.ht

I'm not a lifelong resident of Chicago either, so I know how confusing it can be!  The locals just don't understand how I can still manage to get lost sometimes, but I'm learning as I go.  

Gold Coast is basically downtown.  If you are staying at any of the big hotels downtown, it shouldn't be more than a quick cab ride.

There are quite a few neighborhoods downtown with names that mean something to the locals, but I honestly can't tell where one starts and another begins.  For me, stuff is either really close to the tall buildings, sort of close to the tall buildings, or a potential traffic nightmare away from the tall buildings.  Of those, Gold Coast is really close to the tall buildings.

GPS is my friend.

Walton St. (south)  
North Blvd. (north) (North of North Blvd. is where Lincoln Park (the actual park) begins
Clark St. (west)
Lake Michigan (east)

People try to stretch things and take the boundary south to Chicago Ave. or even further, but that is properly refered to as Near North, which includes River North (Chicago River to Chicago Ave.)

"Downtown" is south of the river from Michigan Ave (east), Congress Parkway (south), to the Chicago River (west).  It includes The Loop, which technically is only the area that is encircled by the elevated CTA tracks.

Hope this helps.  Enjoy your stay