CLASS "A" AIRSPACE
-Class "A" Airspace is from 18000' to FL600 (60000')
-NO VFR OPERATIONS IN CLASS "A"

CLASS "B" AIRSPACE
-The airspace from the surface to 10,000 feet that surrounds the busiest airports in the U.S. The configuration is often referred to as resembling a "upside down wedding cake." Each one of these guys is a little different, depending on the airport's configuration.
-You can't fly in this airspace without a clearance from ATC (Air Traffic Control).
-You can operate VFR in this airspace, however you must have a clearance from ATC to do so. You must have 3 miles of visibility, and remain "clear of clouds."

CLASS "C" AIRSPACE
- If "B" stands for "Big Cities," let "C" simply stand for Cities. The cities under class C airspace are our mid-sized cities. The towers at these fields are equipped with radar -- something that smaller controlled fields (Class D airspace) do not have. Ultralights may not fly in Class C airspace without special permission from ATC. Although the city involved may not be as big as New York or Washington, D.C., it will usually have heavy jet and commercial traffic coming and going.

CLASS "D" AIRSPACE
-For all intents and purposes, the airspace set aside for airports that have control towers.
-This airspace is from the surface up to 2,500 feet, and the radius is usually five miles.
-There may be "keys" that extend out from the circle.
-You can operate VFR in this airspace, however you must establish two-way radio communications before entry. You must have 3 miles of visibility, and remain 500 feet below, 1,000 feet above, and 2,000 feet horizontal distances away from clouds.

CLASS "E" AIRSPACE
-This is a complex definition because it covers the rest of the airspace not designated in above Classes.
-If it is Controlled Airspace, and it is not A, B, C, or D, then it is Class "E". All of the Airways (the "V Routes") are in this airspace. Unless otherwise designated, like the "V Routes" for example, it commences at 14,500 feet and extends up to 18,000 feet.
-You can operate VFR in this airspace, however you must have 3 miles of visibility, and remain 500 feet below, 1,000 feet above, and 2,000 feet horizontal distances away from clouds.

OTHER AIRSPACES
PROHIBITED AREAS
-These are designated for national security, or national welfare. For example, The White House has one. You cannot fly in them. Period.

RESTRICTED AREAS
-A catch-all category. These cover everything from test flight areas, to missile tests and artillery or aerial gunnery. This kind of stuff could hurt you. However, the area may or may not be "hot." You will want to check with the nearest ATC facility to find out. Usually they spend more time being inactive than active.
-If the area is inactive, you are perfectly legal to fly VFR. If you are IFR, ATC will not allow you in if the area is "hot."

WARNING AREAS
-Usually extending from three miles off of the U.S. coastlines and outward. -They contain "....activity that may be hazardous to nonparticipating aircraft." -That's enough to keep me out of them.

MOA's, MILITARY OPERATING AREAS
-This is where the guys, and gals, that protect us in our sleep practice.
-They can be of any size, and shape.
-If you are IFR, ATC will provide the proper separation. If you are VFR you can plow right in.
-It is strongly suggested that VFR operations contact the controlling facility to check on the MOA's status. ATC will provide separation for VFR flights that contact them.

ALERT AREAS
-This is similar to an MOA, different only in that aircraft operating in the area must observe all of the established rules and regulations- both the participants, and those transiting the area.

CFA's, CONTROLLED FIRING AREAS
-This is the only controlled airspace that is not charted.
-This is so because "they" cease all activity when spotter aircraft, or ground controllers see an aircraft entering the area. Truly, ignorance is bliss.

ADIZ, AIR DEFENSE IDENTIFICATION ZONES
-These are over the water, along the East Coast and West Coast, around Hawaii, Guam and all around Washington DC.
-They are there to protect the country from a marauding fleet of bombers, or the individual flight bent on attacking the mainland.
-If you are IFR, ATC will handle the coordination with the military. If you are VFR, flying say from Bermuda to the East Coast, you must file a DVFR flight plan. If you don't tell the Feds who you are in advance, count on seeing a man in a helmet flying close formation with you.

Works Cited:
-Stoen, Hal. "AIRSPACE." stoenworks.com. August 2001. 12 Dec 2007 .