> Right. So trace rays, let them bounce off diffuse surfaces at
> semi-random angles, and gradually total up the results for all rays?

Basically yes. Although there are many ways to reduce the amount of rays needed
to achieve certain noise level without affecting "unbiasness". The point is
that the rays keep on going without stopping them artificially.

> Presumably that won't work with point-lights though? (You'd never hit any!)

There are no point light sources in real life. They always have some volume.
Even a small one. But as mentioned, there are methods to allow them and also
speed up rendering. Like bidirectional path tracing.

For the same reason path tracing works well for outdoor scenes. See image
section for an example.

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