Bhautesh, HSK 63 is originally a German specification. H hollow, S short, K taper. 63 is the diameter of the flange, 63mm.
This is a good spindle nose because the taper has full contact with the internal taper of the spindle nose. Also, the flange is pulled against the spindle face. Consequently, the HSK system is more rigid than other taper type system such as NMTB, ISO or MORSE tapers.
The HSK system is also a good high speed system. They are generally balanced for high speed machining as well.
This system is a bit expensive. You will have to decide how rigid your spindle really must be and how fast it will be rotating.
Hope that helps, Dick Z