What type of renderer is Cycles?

Asking because I seem to be getting conflicting info. Is Cycles a Ray Tracer or an Unbiased renderer? Both?

Tracing; path tracing or branched path tracing.
Biasing; visually unbiased, mathematically biased (it has multi importance sampling, clamping, and everything else that makes it biased). I believe also russian roulette biases it towards biased, and this one is out of our hands. We can turn off MIS, not sure anyone would want to though.

Well, that’s my view on it anyway.

I’m given to understand that Blender Internal (BI) is a ray tracer, since it follows a ray of light from a light source to determine what it hits. Conceptually, a renderer like Cycles – a path tracer – goes the other way, branching out from an object to discover the light that hits it.

Internal and Cycles both follow paths per pixel outward from the camera… the difference is Internal only generates one path per pixel - if it hits a reflective service it bounces off, otherwise it looks to see if a light is hitting it… whereas cycles generates - by default 128 - paths and calculates so many bounces.

I found this very helpful in it’s explanation: https://www.youtube.com/watch?v=Qx_AmlZxzVk

I think cycles is a Monty Carlow render.