"gtlds" means "generic Top-Level Domain" and the "s" means that there are more than one. It also means "generic domain name extension" and a simple way to say it would be "domain name extensions".
I am happy to explain why we talk about "new" gTLDs: "new" means "recent" and when it comes to domain name, we make the difference between "old" domain names such as ".com" and "new" domain names which were published in by ICANN in June 2012 (new domain names from the ICANN new gTLD program).
".com" domains are now hard to find and the trends tends to go to new gTLDs since they are more descriptive. I like to give the example of ".club" domain names which are specific to all kinds of clubs and in any languages. I also like to refer to ".gdn" new domain names which mean "global domain name": an alternative to old ".com" domain names.
I prefer .gdn right now cuz of the prices offered at dotintra & 101domain and cuz so many names are available since its still a relatively new to the market