Testing is critical before launching into the site as there will be issues that need to be fixed before the live stage.
The site will be uploaed to a test server this will allow anyone you share the link with can view it and give any feedback.
This stage the site will be reviewed on multiple browsers (Chrome, Firefox, Safari etc), devices (laptops, tablets, and mobile).
This phase will require final amends to design elements, interactivity and any other features and the overall the user experience. Moving the website to its live Web server. Testing in this environment is important as the live server can have different features than the test server.