you got 2 options
option 1 is using a free sub domain ( yourdomain.dehost.org as example)
option 2 is buying your own domain name ( dehost.org as example)
the first option is free (mostly , exect some co.cc domain names)
the second option is around 10$ for 1 year
if you want a domain name , you can search for a registrar on the net or you can register it by me ^^
please note , not all domain names are avaible, a domain name need to be unic for his extension
let me give a example
powerchaos.com is taken , powerchaos.info is taken , so you can only register powerchaos.org
but i wont do that to prevent problems with copyrights
exept if the owner (hte longest existing domain extension , in this case .info ) or if it is a company (a valid reason needed) then you can register/claim the domain name
but that info is kinda useless for you at this moment as you do not apply for it anyway
to make it short
a free sub domain is yoursite.dehost.org
a TLD (Top Level Domain) is Dehost.org
a subdomain can be found by freehost providers (like

)
a top level domain can be registered by a registrar (

)
hopely this explained what you was searching for
Greetings From PowerChaos