The term "dynamic" refers to any microphone where the source of energy for creating an electrical signal is the sound wave itself. This category includes moving-coil, ribbon and moving-plate designs (used in espionage!). A dynamic microphone is inherently low impedance and so does not usually have a buffer between the electrical element and the cable, but there is often a step-up transformer to increase the output amplitude at the expense of a higher output impedance.
The most common type is the moving-coil microphone, which picks up sounds when sound waves strike a diaphragm attached to a coil of wire. When the coil moves within the magnetic structure of the microphone, it creates an output voltage. The process is exactly the reverse of the way a speaker operates. Moving-coil dynamic microphones tend to be extremely rugged, making them well-suited for most sound reinforcement applications. The other common type of dynamic microphone is the ribbon mic. See ribbon microphone.
A type of microphone that consists of a diaphragm connected to a coil that operates in a magnetic field. Any movement of the diaphragm due to sound pressure levels moves the coil within the magnet, thus producing an electric current. Dynamic microphones do not require external power to operate, are generally more robust, and therefore favored for live use (although several manufactures are making condenser microphones specifically for live use.) The downside is that due to their construction, dynamic microphones are less sensitive to fast transients and don't have the high frequency response of the condenser variety.