I'm aware that I keep blogging about "FBOs" but I'm not sure I've ever explained exactly what one is. When I'm talking to people outside of aviation, I sometimes substitute the words "airplane gas station" but that phrase really doesn't adequately describe an FBO.
First off, as you figured out already from the title of this entry, FBO stands for Fixed Base Operator. I think technically any business that provides aviation services on the airfield: maintenance, flight training, airplane washing, or fuelling is a Fixed Base Operator, but when someone says they are going "to the Eff Bee Oh" they are referring to a business that will at minimum fuel their aircraft, and probably provide many other services. If all they do is provide fuel, then I'll probably call them either "the self-serve fuel pump" or "the guys with the fuel truck." But if they offer any other services, even as basic as washrooms and a table for flight planning, then they become an FBO.
A small FBO may be just washrooms and a bulletin board, but in a town of any size I expect a flight planning computer with an internet connection and someone who can arrange ground transportation and hotel rooms. At the high end you might see a pilots' area with TV, internet, a pool table, a weight room, sleeping bunks, a flight planning room equipped with charts and subscriptions to non-government online weather briefing products, and office facilities. They usually have deicing if that's needed in their climate, and can provide a GPU--Ground Power Unit--to help start an airplane on a cold day. You can also order ice, catering and other things passengers might need and often they have rental cars. I expect an FBO to be able to provide me with the telephone number of a local mechanic, and often they have their own repair facility. This is especially nice when you have a very minor problem like a loose wire causing a gauge to not register, or a stuck fuel cap.
If there are multiple staff, the first people you see are the line guys. Sometimes there is a gal or two among them, but the typical division of labour has the guys running around outside, showing you where to park, pumping gas, and helping you with your luggage, while the females work inside in heated or air-conditioned comfort, behind a desk. Their jobs include answering the phone and radio, arranging things for you and printing out your fuel bill. The line guys often also get to be the shuttle drivers.
If the FBO is a Ma & Pa operation, then Pa pumps gas and Ma collects your money inside. It's not a bad little retirement business for a couple. If it's a small airport and they own the building then I guess overhead is fairly low. If it gets busy it shouldn't be too hard for them to hire an airplane-mad kid to help, and if it's quiet they can spend more time just chatting with the visitors. I'm sure I'm being very naïve and that there is far more to it than that, but hanging out at the airport saying hi to people who come by might still be fun.