All themes are stored within the public/themes directory. Let's look at what a typical theme directory structure will look like, and explain each part of it:
public/
|-- themes/
|-- your-project/
|-- assets/
|-- css/
|-- theme.css
|-- img/
|-- js/
|-- main.js
|-- theme.js
|-- sass/
|-- views/
|-- layouts/
|-- public.blade.php
|-- partials/
|-- header.blade.php
|-- footer.blade.php
|-- index.blade.php
|-- theme.json