The waveform is video’s answer to the histogram. Like a histogram it shows the brightness levels throughout your image. Also like the histogram, it can be confusing to those new to video or colour correction. While the information displayed is essentially the same, how it displays it is very differently.
This video from Aputure walks you step by step through what exactly the waveform is and how to interpret it. Once you learn how it works, it lets you quickly and easily see under or overexposure as well as colour or white balance issues. And when you are used to it, you won’t want to shoot or edit without it.