Hanja
Although a phonetic Korean alphabet, now known as Chosŏn'gŭl or Hangul, had been created by Sejong the Great, it did not come into widespread official use until the late 19th and early 20th century. Thus, until that time it was necessary to be fluent in reading and writing Hanja in order to be literate in Korean, as the vast majority of Korean literature and most other Korean documents were written in Literary Chinese, using Hanja as its primary script. Today, a good working knowledge of Chinese characters is still important for anyone who wishes to study older texts (up to about the 1990s), or anyone who wishes to read scholarly texts in the humanities. Learning a certain number of Hanja is very helpful for understanding the etymology of Sino-Korean words, and for enlarging one's Korean vocabulary. Today, Hanja are not used to write native Korean words, which are always rendered in Hangul, and even words of Chinese origin—"Hanja-eo" ()—are written with the Hangul alphabet most of the time, with the corresponding Chinese character often written next to it in order to prevent confusion with other characters or words with the same phonetics.
Transcription into Korean
Korean has seven consonants that can occur at the end of a syllable and that are used in transcriptions. Those are /p/, /t/, /k/, /r/, /m/, /n/ and /ŋ/. /p/, /t/ and /k/ generally represent foreign voiceless consonants, although /p/ and /k/ (rendered using jamo ㅂ and ㄱ) occasionally denote voiced consonants, too. E.g.: "lab" and "lap" → 랩 "raep"; "deck" → 덱 "dek". Foreign /t/ is variously rendered as ㅅ or 트 "teu". E.g.: "secret" → 시크릿 "si-keu-rit; "set" → 세트 "se-teu. Foreign /p/, /t/, /k/ are rendered using jamo ㅂ, ㅅ, ㄱ if the preceding foreign vowel is short, but generally using 프 "peu", 트 "teu", 크 "keu" if that vowel is long or a diphthong. E.g.: "map" → 맵 "maep (Japanese マップ "ma-p-pu), but "mark" → 마크 "ma-keu (Japanese マーク "ma-a-ku) and "type" → 타이프 "ta-i-peu (but also 타입 "ta-ip) (Japanese タイプ "ta-i-pu). Foreign /l/, /m/, /n/, /ŋ/ are always rendered using jamo ㄹ, ㅁ, ㄴ, ㅇ, regardless of the quality of the preceding vowel. E.g.: "Tom" → 톰 "Tom; "time" → 타임 "ta-im".