Simran Jeet :
if ur not overclocking it so this is your answer
if u building your pc for gaming then u dont need any aftermarket cooler
but if u building a pc for animation, video rendering or video editing then u need a aftermarket cooler
That's the basics but it's a bit more than that.
Different CPU's have higher GHz and clock speeds just on standard. E.g. the AMD fx8350 has higher GHz and produces a lot more heat and the stock cooler that comes with it is rubbish at keeping it cool and that just on idle.