Not much at all, all .vue files in the components directory gets registered globally, so if you create a Navbar.vue file, you can use <Navbar /> anywhere in your theme. Easiest templating system I've ever used. If you learn a bit of how passing props work, you're golden!
Some info on vue single file components: https://vuejs.org/v2/guide/single-file-components.html
Props documentation: https://vuejs.org/v2/guide/components-props.html