TLD (top-level domain)
The top-level domain is the part to the right of the last dot. There are country-code TLDs (ccTLD, e.g. .de, .at) and generic ones (gTLD, e.g. .com, .shop). Each TLD has its own registry and its own rules.
How it differs: ccTLDs are assigned to countries/regions, gTLDs are thematic/generic.
Example: in "example.de", ".de" is the TLD.
Further reading: guide