A generic Top Level Domain (gTLD) is a domain name extension. Once that are most common and familiar are .com, .net, .org and so on. In October 2013, there were roughly 22 gTLDs available. Soon, there will be roughly 1,400 released. About 700 of them will be released to the everyone, while the other trademarked ones (such as .nike or .ibm) will not be available to the general public.
Infographic by: webmechanix.com