Grails is not only a web framework but a complete development framework which runs on top of JVM.It uses convention over configuration which makes it different from most of the frameworks which require alot of XML configuration. There is no need to use XML to configure various things while creating an web app using Grails. When application is created initially using Grails, it creates various directories in the project which are meant for specific things. For example , it creates folders like spring,hiberante,domain,controller etc where the specific files should be placed and application will automatically pick those up.Also Grails provides utilities to create domain classes and controllers which gets created and also gets copied to the directories which are meant for them. Isn't this wonderful. This saves alot of development time and is the beauty of framework.