It looks like it is a set of components and helpers for building components of your own.

The good thing about Web Components is that they are reusable across frameworks. You don't need jQuery-picker, react-datepicker, and vue-datepicker just <my-datepicker /> and its reusable anywhere.

I work in an org that is looking to provide a lot of the same experiences both within salesforce and outside of it, and I'm looking at this make sharing those components easier. Imagine if you have a calculator and it could be used by both your client relations team (working in salesforce) and on your retail-facing web site.

right now we write two UIs and hook them up the same service. now maybe we get to write one UI.