What are some popular slang and text words in Korea? something like ㅋㅋand ㄱㅅㄱㅅ
I watch a lot of Korean dramas, variety shows and Kpop videos. There are a lot of terms and phrases I don't understand and I can't find them in books because they are informal.

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Answer

ㅋㅋ is laughing! like laughing sound 'kk' 
For example, 'ㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋㅋ' is laughing loudly.
'ㄱㅅㄱㅅ' means thank you. It is based on '감사'. It means '감사감사'.