Getting good quality audio is often the biggest challenge faced by DSLR & mirrorless video shooters. The microphones built into most cameras are notoriously bad. They hear all kinds of background noise and echo, they hiss, and pick up a lot of unwanted sound from the camera itself, like autofocus (or even manual focus adjustments).
The easiest solution, of course, is to use an external microphone. You can then plug this either straight into your camera or a separate portable field recorder. While there are many different types of microphone out there, sometimes a lavalier is your best choice. This is where there Saramonic UwMic9 dual wireless lav mic kit comes in.