Buefy (pronounced /ˈbyo͞oˌfī/, like beau-fy) is a user interface component library made on top of Vue.js and Bulma; two fresh, but well-known, frameworks. Buefy has two core principles: 1. keep stuff simple and 2. be lightweight.
We like to think that Buefy is the javascript layer for your Bulma interface, since it doesn't require for it to be a sophisticated Single-Page Application. You can import it completely or single components on a ordinary webpage and use Vue.js as a replacement for jQuery — as you can see in this Codepen or any other example over the documentation.
This documentation assumes you know the basics of Vue.js, if you're not comfortable with it yet, it's probably not the best idea to learn from here as your first step — learn the basics then come back. Vue.js website is the best source for you to start with.
Now that you know what Buefy is, get on to the next step and install it!