Each country is assigned with a country-level domain to know the address of any domain name. For eg, Nepal is assigned .np and India is assigned with .in country-level domain.
The first registered country level domain was .no, which was registered in 1983. Later other countries that registered were .us, .uk, and .il in 1985, then followed by .au, .de, .fi, .fr, .is, .kr, .nl, and .se were also registered in 1986.