The preceding preedit region contains five Hangul syllables that have not yet been committed. That is, they have not yet been added to the text block being assembled for the application.
These syllables could be committed to the application by typing Control-K. This nonprinting character is not committed in the input along with the syllables, for example:
Otherwise these syllables could be committed by typing the Space bar or a number, punctuation mark, or other printable character that is not part of a valid Hangul character. Unlike Control-K, a printable character (like a question mark) is committed in the input along with the Hangul syllables, for example: