Hi, what can I use it for?
Heyho
well you can let it show you what the printer is doing (more or less) at the moment and you can check out other layers. 
It's like the preview in your slicer but in 2D and you look at it from above
I just like watching it. 
It is useful to see what is happening on the printer right now. As my camera is setup the video feed doesn't always give enough detail.
I also like to use the sliders and Next Layer / Previous Layer buttons to see what is coming up in the next few layers of the print.