404.liquid template renders a page where visitors are taken to if they enter an invalid URL for the shop.
Give the visitors some options on how to proceed
When the visitor is presented with a 404 page, it should be made clear that the page they were looking for was not found. Furthermore the visitor should be given options on what actions to take next. For example, you can add a link to the home page, or a search bar (to see how to include a search bar into a template, see search.liquid).