Short answers, pulled from the story.
King Sejong the Great personally developed the alphabetic featural writing system known as Hangul during the 15th century. He introduced it in a document called Hunminjeongeum to promote literacy among common people.
The linguistic homeland of the language is suggested to be somewhere in contemporary Manchuria. This region served as the starting point for proto-Koreans who expanded into the southern part of the Korean Peninsula around 300 BC.
Modern Korean uses 24 basic letters called jamo plus 27 complex letters formed from the basics. These letters form the core structure of written syllables alongside consonants and vowels.
North Korea abolished Hanja in writing in 1949 but continues teaching them in schools. Today Hanja is largely unused in everyday life though still important for historical and linguistic studies.
More recent loanwords are dominated by English accounting for approximately 90 percent of non-Sino-Korean borrowings. Konglish describes English-derived Korean increasingly used throughout society.