It's a camera with a fibre optic lens that you can poke down small holes and around corners to see into place that normally you can't. Plugs into your clever phone and you can see what the camera is seeing on the phone screen. Much like the cameras that Dr.'s stuff into you to look at your insides.
I've used borecams for work. They were originally conceived to inspect the insides of jet turbines. They work great for that kind of work, small places with shiny surfaces. They can't throw a lot of light by themselves so if you use them inside something like a steel air receiver with surface rust, you can't get much of an image at all because the light can't reflect very well. So they can be good if you can supply auxiliary light sources. I have a Jaycar borecam and I used it to look inside the side tank of my dinghy when I cracked the chine. I had to put a torch in first to get enough light for an image. The industrial cameras have external light boxes with HID lamps that send light down the tool by optic fiber.
The fiber part is either quite stiff or really floppy. It can be tricky to work out how to get the cam end pointing the right way on the inside of something! Even if I find what I'm looking for, it'll end up on some weird angle on screen.
Focal length can also be an issue. Hard to get the tip just the right distance from the work to get focus.
Now days though, it can be easier to shove a GoPro inside things on the end of a selfie stick if it will fit.
The drain cameras work well by using a spider to hold the camera in the middle of the drain. You can also fit a lot of LEDs on a spider for a 2 inch drain.
On the other side, I use them to look for pitting type corrosion etc. If you just want to spot a liquid level in a tank or confirm a block in a drain, that kind of job, the light issue isn't as critical.
I hope that provides some background info. If your job suits a borecam, they are awesome.
