The most important meanings of 지내다 are as follows. 1. 살다. Pass a period time. Live (through a period). (잘 지내니?) 2. associate with someone; be on good or bad terms with someone. (친구와 사이좋게 지내거라.) 3. 역임하다. Serve in an official position (used on in past tense only). (그 사람은 국무총리를 지냈다.) Although 지내다 (#1) has a similar meaning as 살다, the two are usually not interchangeable because 살다 is not used much in casual senses as in greetings. It is about getting by in a day-to-day life while 살다 has more serious and higher level meanings. 요즘 어떻게 살아요? is very rare as a greeting, although it might be heard in certain special circumstances. Examples: - 요즘 잘 지내세요? - common greeting. 잘 사세요? would sound strange. - 걔네는 결혼해서 잘 살고 있어. - '살다' here means more than just day-to-day life, like adjusting to the new life style, not having trouble in the marriage, etc.