Gojoseon was what Korea was called in ancient times. It is called Gojoseon because "Go" is ancient in Korean and
Joseon because Joseon is the English spelling for the Korean word for "Korea". It is also called Choson but it is called Gojoseon to distinguish it from the more modern Joseon Dynasty which started in 1392 and ended in 1910.
Gojoseon, ancient Korea, was founded by ancient Manchurian tribes from Northern China. According to legend, it was founded by a demigod named Dangun Wanggeom who was "the grandson of heaven". His father, Hwanung, was the son of Hwanin, lord of heaven. His mother was a shaman woman from an animal totem tribe. The Gojoseon kingdom was founded in 2333 BC and lasted for thousands of years. Gojoseon was still a kingdom in 108 BC and was famous for having a war with the Han Dynasty of China.
The people of Gojoseon spoke "Proto-Korean" an early form of modern Korean. They also had a shamanistic religion like the Zhou Dynasty. They worshipped animal totems. They went into the iron age around 300 BC.