What is END and NED?

Simply put,

END = Evidence of no defect
NED = No evidence of defect

Let us talk about each of them.

Is is possible to achieve END? Does any application or program exist that have no defect? Practically speaking, no. In a complex application there are lots of controls an interdependent modules. Testing each and every bit is not possible practically. So it cannot be assured that there is no defect in the application. Whatsoever, amount of testing we do on the given application.

But there is another school of thought who says it is possible to achieve END. Consider the program written in C below:

int main()
{
printf("hello, world");
return 0;
}

It simply prints hello, world on execution.We are 100% sure that the line will be printed, without any fail. So the evidence of no defect or END is achieved.

Now comes NED. What does it signify?

Having no evidence of defect means -- you have conducted your testing based on your test scripts. You have covered all the possible areas, you might. Based on the set test cases and the scope of testing you can say that the application passes your test. In other words, there is no evidence of defect in the application.