Mods, This is a very common question. Please sticky.
There are quite a few balanced mics out there; NTG-2, SGM-1X etc. So why go balanced?
Balanced audio is a method of interconnecting audio equipment using impedance-balanced lines. This type of connection is very important in sound recording and production because it allows for the use of long cables while reducing susceptibility to external noise.
If you're recording to a camera (XH-A1) or recorder (Zoom H4/n) which has a balanced input, you're good to go. Just connect your mic up with an XLR cable and you're balanced.
If, however, you want to record to an unbalanced device, HVx0, zoom H1, H2. You'll need to terminate the balanced signal to maintain protection from signal interference.
You can use an XLR audio adaptor like the Juicedlink:
You'll find a lot of useful information (see learn stuff), about getting better sound, here as well as product info.
These adaptors will keep your cable run balanced and provide other pluses (pre-amp, independent gain control between channels). But there is a lower cost option which will terminate the balanced signal:
Such transformers use a simple balun:
A type of electrical transformer that can convert electrical signals that are balanced about ground (differential) to signals that are unbalanced (single-ended).
What about mating the XLR cable to a 3.5mm jack with a simple converter, that works too, right?
Yes, it does work but, because the adaptor grounds out a phase, the signal won't be terminated properly. So your whole cable run will be unbalanced and, therefore, susceptible to signal interference.