TLD stands for top-level domain. It is the final component of a domain name, like .com.
ccTLD stands for country-code top-level domain. It is a subcategory of TLDs used to identify a particular country – for example, .co.uk, .de, .mx, and .fr are all ccTLDs.
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 domain extensions has been expanded with the addition of TLDs like .online, .xyz, and .name.