There are many Korean words, which entered Korean through Chinese. In Korean, they call these "한자" (hanja); the "한자" is the Chinese character itself.
People will use the Chinese character (the 한자) to differentiate words, since lots of them sound the same after porting into Korean.
바다 is a native Korean word meaning sea/ocean.
해(海) is a 한자 word with the same meaning.
And for one example, 해(害) is a 한자 word that means "harm, damage, evil, injury".
Eojjieojji georeo badaewane I badaeseo naneun haebyeoneul bwa Musuhan moraealgwamaeseopgo geochin baram Yeojeonhi naneun samageul bwa Badil gajgo sipeo neol ontong deurikeosseo Geunde geujeonbodadeo mogi malla Naegadaaneun geosi jinjeong badainga Animyeon pureun samaginga