훈민정음 해례본(Hunminjeongeum Harye): 1446, by King Sejong, 한글 proclamation.
This is the original book about hangul, including the 어제(preface) and 예의(samples and significance) section, which made up the core part. It was written in 한문 (Chinese) which was the official script at the time.
훈민정음 언해본(Hunminjeongeum Eonhae): 1457, under King Sejo, translated version.
This version comprises the 해례본 and annotations as well as 한글 translation of the 어제 part of it. This version is very important for the study of old Korean as it is the earliest text written in Korean.
There is a Wikipedia page with more detail on the above: