Nowadays, most people sleep for around eight hours, give or take some, in a single stretch. This is what's called monophasic sleep.
But monophasic sleep isn't the only way-- and, as an increasing amount of scientists and historians believe, it isn't the most natural nor healthiest option.
Enter polyphasic sleep-- an alternative to monophasic sleep that's become more prominent over the past few years. Whereas monophasic sleep means sleeping in a single stretch, polyphasic means sleeping in two or more stretches. This allows people to sleep less than they would otherwise need to, have more free time, and feel more awake throughout the day. Some polyphasic cycles mimic natural cycles, some mimic historic, and others represent deliberate ``hacking'' to eek out every ounce of efficiency and time possible to eek.
Whatever kind of cycle you want, there's probably a good polyphasic one for you!