GTLD

GTLD stands for Generic Top Level Domain Here is a list of a couple of GTLD.

GTLD	Description
.COM	.COM is one of the original TLD's. It's operated by Verisign. It was created 1985. It's for commercial usage worldwide.
.NAME	.NAME is operated by Global Name registry. The intended usage of the .NAME was for personal sites for individuals
.NET	.NET is operated by Verisign. The intended usage of the .NET domains was for network infrastructure.

There are more domains. You can read all about different domains under TLD.