CREATION OF HANGEUL

한글 (romanized as Hangeul) is the Korean "alphabet".
This writing system was introduced in 1446 AD by King Sejong the Great. Before this, in Korea, everything was written in Chinese, which was difficult to read, so the majority of Koreans was illiterate.
자모 (romanized as Jamo) are Korean "letters". They're so easy because they were created by imitating the shape the mouth assumes while pronouncing a specific sound.
If you don't know Hangeul, click here to get to its dedicated section.