bluemax, the interchangeable "heads" (capsules, actually) fit onto one common body (amplifier, actually) and let you use any of three different directional patterns (in this case, omnidirectional, cardioid and "shotgun") at will, without having to buy three separate, complete microphones.
That's the whole idea of a "modular" microphone system; most major microphone manufacturers have systems like that. One manufacturer offers twenty different capsule types with different patterns and/or frequency response characteristics; others have from two to seven different capsule types. Some manufacturers have accessories that go between the capsule and amplifier, and allow for various configurations that offer practical advantages, such as "active cables" for stealth mike placement. This approach lets you buy whatever you need most at first, then add new capsules and accessories to widen your range of technical capabilities, without having to pay for the same amplifier components over and over.
Small-diaphragm condenser microphones with basically neutral/transparent sonic characteristics aren't limited to any one "preferred" application--they are suitable for nearly all applications. You may find that for certain applications you'll want to EQ the result, but that's OK; neutral/transparent microphones generally take EQ much better than microphones that already have strong, stubborn "opinions" hard-wired into their response characteristics.
--best regards