First of all, we need to create a method in the SiteController as like
def about() { def page_title= 'About page' def page_description = 'This is complete tutorial to build an application using grails 3.x. There is several parts of tutorial where every part has a specific objective and several steps. So it is a step by step tutorial to build a complete application using grails 3.x'; render(view: "about", model: [page_title: page_title, page_description: page_description]) }
After that we have to create a view under grails-app/views/site/ which name is about.gsp
Browse this about page : http://localhost:8090/site/about