Mesh - Bridge Mode? What is it?

[NeilF]

So if you're plugging a Mesh "router" into your ISP's router, you turn the ISP's Router's wifi off, and then the Mesh unit takes over all things wifi.

HOWEVER, I'm somewhat confused about "Bridge Mode". I'm guessing with the above setup, you would have the mesh router in "Bridge Mode" as you're letting the ISP's router control IP addresses and the like?

Have I understood that correctly? I've read a few descriptions and I've failed to come to a clear understanding.

If I have understood it correctly, the question is, why would anyone not be using "Bridge Mode" as surely most folks do plug them into an ISP's router which offers the internet connection?

 

[NeilF]

In my case we're talking about s Sky Q Router.

Is my understanding correct btw? To stop two routers fighting and confused who's in charge, you set the mesh router to bridge mode.