Defect Density will show how many bug is available in KLOC
like tester will find 650 bug in 10000 line
it means  6508*1000/10000 = 65 bug in KLOC
it will show capability of developer
it will also define quality of product
some organization will release  produce according to Defect 
Density like .5 in KLOC

Defect Density = no.of Bugs/KLOC
It indicates that how many number of bugs u find for ever 
1000(kilo) lines of code.