In korean, there are lots of different conjugations which still have the same meaning; For example, -이건 뭐지? -이건 뭐야? -이건 뭐냐? -이건 뭐? -이건 뭐에요? -이건 뭡니까? -이건 무엇입니까? -blah blah blah… We still have more to come...(duh??!!!) The above are all the same meaning sentences. I’d rather explain by making examples in English. 1. 이건 뭐지? - What the heck is this? 1. 지 - the heck 2. 이거 해야지! - (I’ve) Gotta do this! 2. 지 - (have) got to