The home.twig view renders the home page of your theme. It's loaded when you go to the root / of your website.
The home page will usually present the visitor with a range of information about your website and the products that you have for sale.
You may like to include featured products and/or featured categories using the appropriate functions.
The trend at the moment is also to include a hero image, or number of images, at the top of the page. These can be dynamically rendered from the galleries feature of the account and rendered on the page using the settings.json file and by following the instructions in this article.