What, you may ask, is a gTLD?
Let’s start with TLD. Top Level Domain. This is the highest level in the naming scheme used for websites (domains). The best known TLD is .com. Other common ones are .biz, .org, .info, .net. There is even a .xxx.
gTLD stands for generic TLD, as opposed to ccTLD. ccTLD is a country code TLD. There are over 200 ccTLD codes and 22 generic ones.
To see a list of all the gTLD and ccTLD coes, visit this page.
To complicate things, a large number of new TLDs will start popping up next year after an auction is held. You will see ones like .music, .book, .hotel, .app. For a complete list of all the proposed new ones, see this page. The difference with the new ones is that they will initially be owned by individual corporations or organizations.