Hi Vanishree,
Thank you for your question!
All-pairs is a method for finding what configurations to test. When you want to test bugs in a program you know that some of them will be influence by the interaction between pairs of parameters. Finding and deal with them can be harder and more expansive and this is where combinatorial testing technique enters.
When you choose the right test vectors you can do it much faster and in a systematically model you cover more possible scenarios. This way you know you most likely will not forget to test parameters that influence one another.
We are planing on writing a more detailed article about it and I will send you a link to it when it is done.
Thanks for your question!
STTools Team.

Hi Someone!
It depends on what your looking for exactly. What and how would you like to test?
You can look in this article for open source test management tools
Good luck!

Hi,
Not every project needs testers, but every project needs testing. In many projects testers are aimed at validating the functionality and compliance of the system, while at other projects the programmers are the ones who take this responsibility and they test the system using any means that stand at their disposal. You can read about Test Management – functionality list in the link.
Hope this answer your question!
Enjoy!