The term handheld microphone generally means any microphone that's supposed to be held in the hand while picking up sound. Handheld microphones are used in a huge variety of settings, from musical performances to television interviews.
A cardioid microphone has the most sensitivity at the front and is least sensitive at the back. This isolates it from unwanted ambient sound and gives much more resistance to feedback than omnidirectional microphones. This makes a cardioid microphone particularly suitable for loud stages.
To capture sound, dynamic microphones use a diaphragm, a voice coil and a magnet. The rear of the diaphragm is attached to the voice coil, which is surrounded by a magnetic field. The sound picked up by the diaphragm moves the voice coil in this magnetic field and generates the electrical signal; an electrical representation of the picked up sound. They can handle extremely high sound pressure levels and are largely unaffected by extreme temperatures or humidity.
A microphone with tailored frequency response is usually designed to enhance a sound source in a particular application. For instance, a microphone may have a peak in the 2 – 8 kHz range to increase intelligibility for live vocals.
3 Pin XLR: The circular 3-pin XLR connector is an industry standard for balanced audio signals.