What is a gTLD?
A gTLD is a generic top-level domain. Top-level domain (TLD) refers to what is to the right of the dot in a domain name, sometimes referred to as the domain extension. Generic means that search engines will see it as generic, i.e. having no regional targeting for searches.
All generic TLDs are at least three characters or more. The original gTLDs are .COM, .NET, and .ORG, which were delegated in 1985. Since then, the number of gTLDs has grown, most recently with the new gTLD delegations starting in 2014.
A gTLD is one type or category of TLD that is distinguished by the Internet Assigned Numbers Authority (IANA). Other TLD categories include country code top-level domains (ccTLDs), sponsored top-level domains (sTLDs) and internationalized top-level domains (IDN TLDs).
In addition, you may see reference to new TLDs (nTLDs) and regional or geographic TLDs (geoTLDs); however these are both unofficial categories because TLDs that fall into these categories are considered gTLDs*. Another unofficial category is gccTLDs, which are ccTLDs that are considered generic.
*Google and other search engines generally consider regional TLDs to be generic for search usage and do not assign any regional targeting to them.