Microphones
The second takeaway is that mics have a directional component or what is called a polar pattern. This means the area around the mic from which sound is picked up. Omnidirectional mics take in sound surrounding the entire radius of the mic. (Your smartphone's mic is omnidirectional.) While unidirectional mics (also called cardioid) are more focused and take in sound from only one direction. Bidirectional mics take in sound from two different directions. Why does knowing this matter? At it's most basic, you want to make sure you are aiming the mic in the right direction to get the best recording possible as having certain mics off axis can significantly impact the quality of a recording.
It's also important to pay attention to polarity when selecting a mic. Do you want a mic that can pick up sound from a lot of different directions without having to change the angle (think press conference)? Choose omnidirectional. Do you want a mic that is highly focused in one direction and reduces background noise (think one person talkinging into a mic)? Choose unidirectional. Do you need to record sound in front of a behind the mic (think recording an interview where one person is on each side of the mic)? Choose bidirectional.