I've found it best explained in some stackoverflow answer mentioning the pet vs cattle analogy. In short, if you know how many servers you have from the tip of your tongue, and what they do more or less, then they are akin to pets: you treat them well and keep an eye on each of them.
Kubernetes is meant for when you have so many of them, that come and go without you even noticing or caring, bearing a number for the sake of production/cost control, this is cattle. Needless to say that this is not your typical app/company running at such a scale, and that there is a 24/7 team of "ranchers" keeping an eye on the herd.

[–] ramius345@sh.itjust.works 3 points 1 year ago (1 children)

https://github.com/kelseyhightower/kubernetes-the-hard-way

[–] CanadaPlus@lemmy.sdf.org 1 points 1 year ago (1 children)

Thanks. So TL;DR it allows you to set up a little cloud computing service on your own physical machines, minus load balancing which you have to add on?

[–] ramius345@sh.itjust.works 1 points 1 year ago

It can be used to scale cloud computing services as much as you want. It's a scalable container runtime at its core. It provides a means for scaling an overlay network with service discovery and uniform ingress configuration.