The article is worded pretty badly, and is clearly written by someone who's had some things explained to them, and then have got a bit confused. "Raytracing" i

The article is worded pretty badly, and is clearly written by someone who's had some things explained to them, and then have got a bit confused. "Raytracing" is a bit of an overloaded term, but conventionally "Raytracing" for graphics meant a serious of "raycasting" events, and "Whitted" style was a technique which could approximate reflective and refractive materials fairly accurately (as long as you modelled the fresnel effect and absorption) in a recursive style. Modifications on top of this are also to do limited indirect rays for global illumination and this was used a bit (in film/CG VFX in hybrid renderers like PRMan pre 19), but doing global illumination this way was pretty slow and didn't scale well (an exponential branching factor at each bounce). So technically, the article is sort of correct on this point, as Pathtracing is more smart about how it handles the full rendering equation of "all" light transport simulation, and is faster than Raytracing for high fidelity (i.e. global illumination, area lights), due to its stochastic nature of sampling multiple dimensions of lights, surfaces, volumes, etc across many samples per pixel. Pathtracing does take reflection and refraction into account, but generally (there's a technique called 'splitting', which sort of branches the paths to make it more like 'Whitted' raytracing, but ignore that for now) it relies on "importance sampling" to make smarter decisions, based off the material response (diffuse, glossy, reflective, refractive), which guides the direction of the next ray off the previous surface. This generally means that due to the "random" nature of pathtracing sampling (it uses monte carlo random sampling), predominant lighting is generally more efficient, although things like caustics, SSS and indirect illumination can still be very noisy as they're hard to sample and can take thousands of samples to resolve to "clean". There are other techniques like Russian Roulette to kill particular paths which don't have much throughput and/or light contributions, which can speed up renders as well, and I think is what the "dumping most or all of the secondary ones doesn't affect things as much as one might think." part is referring to.