@Echo
Yes, we call 漢字 as "hanja"
Actually, there is no hanja in any kind of Korean sentences.
But most of Korean word (over 70%) can be changed into 漢字.
Not using hanja has a fatal weak point.
For example, "정의" can be changed to 定義(definition), 正義(justice), 正意(correct meaning) etc. etc.
We have to think about the context before translating a word.
Korean has a lot of homonyms >_>
Some kanjis have a multiple pronuncations to solve this problem.
But 1 hanja has only 1 pronuncation.
Korean / Japanese are come from Chinese.
The difference is, Korean is a new-language(it's an absolutely different language if Korean don't use hanja) and Japanese is a fixed-language(kanas are based on Chinese words)