After all the schema definitions and the version information in web-app, the display-name tell your servlet container (Tomcat) the site's name for administration purposes, and description likewise.
Then the servlet tag has a servlet-name for you to define your serlvet a name that will be used later in mapping. You'd normally define a Java class under servlet-class also, but we're not creating Java classes in this tutorial.
Finally you set a servlet-mapping, that points via servlet-name to the name of the servlet you defined above, and maps that to a url via url-pattern, '/hello' in this case.
Next you will need a build.xml file to build this via Ant.
We first set the properties for the project. Then we have a blank compile target, that would normally compile your Java classes. And this depends on a prepare target that copies all the stuff in web/, i.e. web.xml and hello.jsp, into the build directory. Run 'ant' to make it do this.
Then you need to deploy this. You'd normally package this up into a WAR (Web ARchive) file, but Tomcat allows you merely to copy the content of build/ into its webapps/ folder (in the location where tomcat is installed, in my case /var/lib/tomcat). You do this via: