This field is the name you assign to your server. It does not have to be the hostname of your computer (though that is recommended). This name will be seen by users when they log into your server, and by other servers networking with your server. It is suggested that you consider that when you choose a name. While you may choose almost any name, it must not have any spaces in it.
/as general set name irc.webmaster.com
It is generally a good idea to have a uniform naming scheme for all the servers on your network, to make it easier for people to remember them. While most people do not need to know the server names, it is important for the network operators who may need to route servers. It also looks nicer and more professional if all of the servers follow the same pattern.