What's the difference between a TLD, gTLD, ccTLD?

TLD: TLD stands for Top Level Domain. A TLD is the last part of the domain name, after the dot. TLD's are managed by ICANN (Internet Corporation for Assigned Names and Numbers). In the early years of the internet, there were 3 main TLD's that were publicly available; .com, .net, & .org (.int, .edu, .gov, & .mil also existed for restricted use). In the past 2 decades, there have been over 1000 new TLD's added.

gTLD: gTLD stands for Generic Top Level Domain. The most common of these include .com, .net, & .org. There are however different categories under this. The aforementioned being generic, along with most of the new TLD's being released these days. sponsored, which includes TLD's like .edu, .gov, & .mil. generic restricted like .biz, .name, & .pro, are restricted to a specified purpose.

ccTLD: ccTLD stands for Country Code Top Level Domain. These TLD's were originally meant to be geographic. They were assigned to each country, and in some cases territories like the Christmas Islands (.cx). Each territory is responsible for how that TLD is used. Most countries use them as their primary TLD (though .com still rules them all), however in many cases, countries/territories have sold or leased their ccTLD, and they have been made available to the public. Many being very desirable due to being only 2 characters, such as .co, .me, & .ws.