A domain class can be created with the create-domain-class command:

grails create-domain-class Person

This will create a class at the location grails-app/domain/Person.groovy such as the one below:

class Person {	
}

If you have the dbCreate property set to "update", "create" or "create-drop" on your DataSource, Grails will automatically generated/modify the database tables for you.

You can customize the class by adding properties:

class Person {	
	String name
	Integer age
	Date lastVisit
}

Once you have a domain class try and manipulate it via the shell or console by typing:

grails console

This loads an interactive GUI where you can type Groovy commands.