What are the two categories and four types of airspace in the U.S.?

3-1-1. General
a. There are two categories of airspace or airspace areas:
1. Regulatory (Class A, B, C, D and E airspace areas, restricted and prohibited areas); and
2. Nonregulatory (military operations areas [MOA], warning areas, alert areas, controlled firing areas
[CFA], and national security areas [NSA]).
NOTE-
Additional information on special use airspace (prohibited areas, restricted areas [permanent or temporary], warning
areas, MOAs [permanent or temporary], alert areas, CF As, and NSAs) may be found in Chapter 3, Airspace, Section 4,
Special Use Airspace, paragraphs 3-4-1 through 3-4-8.
b. Within these two categories, there are four types:
1. Controlled,
2. Uncontrolled,
3. Special use, and
4. Other airspace.
c. The categories and types of airspace are dictated by:
1. The complexity or density of aircraft movements,
2. The nature of the operations conducted within the airspace,
3. The level of safety required, and
4. The national and public interest.
d. It is important that pilots be familiar with the operational requirements for each of the various types or
classes of airspace. Subsequent sections will cover each class in sufficient detail to facilitate understanding.