Hello Murali,
'K' stands for Kilo--but not in terms of the weight measure we-in India-are used to. Kilo also means 1,000 numerically.
So 12K means 12,000 [Rs or $ or whatever the currency is].
Basically it's an American term to denote salaries, since their counting is always in thousands--like 1,000, 10,000, 100,000 [we term this as 1 Lakh], 1,000,000-meaning 1 million [our term for this is 10 lakhs]....& so on.
Now this has become the global standard of terming salaries--thanks to the IT boom :-)
Rgds,
TS