A TLD stands for a top-level domain. A .com, .org, or .pk domain ends with this part.
A ccTLD is a country-code top-level domain. A country-specific TLD identifies a specific country – for example, .com.pk and .co.uk.
A gTLD is a generic top-level domain. Domain names with gTLDs are most common since .com domains generate more registrations than those with ccTLDs combined.