If it’s a controlled airspace, but it isn’t Class A, B, C, or D around airports, it’s considered Class E. Class E airspace is often referred to as the controlled airspace between airports although sometimes it surrounds an airport and starts at the surface. It can also start at 700 feet AGL, 1,200 feet AGL, or 14,500 feet MSL. Class E airspace tops out at 18,000 feet MSL. For all you trivia nuts, Class E starts again at 60,000 feet MSL (Flight Level or FL 600) and goes to the end of the atmosphere. Of course, sport pilots are limited to an altitude of 10,000 feet MSL!
As a private pilot you might be doing much of your flying in Class G (uncontrolled) airspace; or some Class E (controlled) airspace. The good news is that most low-altitude airspace is Class E and G. In Class E and G airspace no radio is required so you’re on your own. That simply means if you have a radio, you will monitor common communication channels for traffic and announce your intentions if you are flying into an uncontrolled airport. (Although a radio is not required, it’s still a good idea to have one.)
Even though Class G airspace carries the moniker “uncontrolled”, remember that VFR minimums apply. If you can’t see, you can’t fly.
"Man cannot discover new oceans unless he has the courage to lose sight of the shore."
-- Andre Gide