TLD stands for top-level domain. It is the final part of any domain like .com, .org or .gov
ccTLD stands for Country Code Top Level Domains. It is a subcategory used to identify a particular country. For example, .co, .uk, .es, mx, .de.
gTLD stands for Generic Top Level Domain. gTLDs are the most common type of domain name. In part because this category includes .com domains, which have more registrations than all ccTLDs combined.
Historically, the main gTLDs were .com, .org, .net, .edu, .gov, and .mil, but the number of available gTLDs has expanded with the result that hundreds of gTLDs are now available, including .online, . xyz and .name