Hangul syllable jaebs

Enter ㅈ, ㅐ, ㅂ, then ㅅ in a Korean IME.

On the standard two-set Korean keyboard, there is no dedicated key for the whole block; the IME builds it from those keystrokes. The final two inputs combine into ㅄ, Hangul’s double final.

what does 잾 mean

It is a Hangul syllable whose word meaning comes from context.

Hangul puts a starting consonant, a vowel, and an optional ending consonant into one block. In Korean, syllables join to form words, so the surrounding text supplies the word meaning; the final consonant or consonant cluster is called 받침.

Hangul was devised under King Sejong to write Korean speech directly, so writers did not have to rely only on Chinese characters. The name of the script, Hunminjeongeum, first appears in the Sejong annals in 1443; a book explaining the writing system was published in 1446. Modern Korean spelling traces to a 1933 proposal, partly revised in 1988. These are dates in Hangul’s history, not a first-use date for 잾.

why does 잾 split into jamo

It can display as separate jamo and still be one syllable. Unicode can represent 잾 as a precomposed block or the canonically equivalent sequence 잾. A font or text path that does not shape conjoining jamo into a syllable may show the parts separately; the text can still represent the same syllable.