If you are shopping around for microphones, chances are you have seen the term Frequency Response all over the place. If you don't know what that means, you've come to the right place. You can watch the video to the right or read the very description below.
To put it simply, frequency response is the range of sound that a microphone is capable of picking up. The way that this measured is using Hertz (abbreviated as Hz). The lower the number, the lower the sound. For instance 20Hz is extremely low, but on the other hand 20,000Hz (also notated as 20kHz) is extremely high. The reason I used these two frequencies as an example is they are the outer limits of what are ears can hear.
Some microphones do not cover this entire range, and that's not necessarily a bad thing. The bane of most audio engineers existence is low frequencies. So if you have a microphone with a frequency response starting at 50Hz, this may help eliminate a lot of the trouble frequencies. The same goes for the high end. A lot of microphones do cover frequencies all the way up to 20kHz, but it's not necessary. One of the most popular microphones out there the Shure Sm58 has a frequency response of 50Hz - 15kHz.
These specifications are well and good, but they really aren't that important unless you have very specific technical needs. What I think is most important is how the microphone sounds to you. So what I would recommend is finding a test video of the microphone you're looking for and seeing how you like the sound and let that information, couple with the specifications, help you decide what microphone is right for you.