For starting learing Korean, I think you must know alphabet and basic expressions!!
1. 안녕하세요 an nyeong ha se yo? = Hello, Good morning~evening
2. 고맙습니다 go mab sum ni da = thank you!
3. 안녕히 가세요 an nyeong hi ga se yo = Take care, Good bye
These are formal greeting expressions and very basic among Koreans.
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안녕 An nyeong has two meanings :
1. 안녕? = Hi?/ 안녕- Bye!
(infromal greeting, / in the case of "bye" we pronounce it more longer. [an nyeooooong])
2. Everthing is fine, good.
=> So, 안녕하세요 means 'everything is fine with you, sir?
그럼 안녕~~