This is part 5 of 15 part series on building web server with go. Checkout https://www.gophersumit.com/series/web-server/ for more. html templates template is what it sounds like. It is a predefined html with placeholders to render data. This template is not directly returned to user, it is first parsed by a component called template engine. The work of template engine involves parsing the html and replacing the placeholders with actual data that is provided to template engine.