Kali Linux is one of the better penetration testing distributions out there. I’ve used Kali to play a bit and i liked it allot, however I’m biased and my personal favorite is BlackArch, it is less well known so I will keep it on Kali for now.
If you want to test your “own” network, you need useful penetration testing tools.
Kali is a liveCD which has allot of them build in, and as it is a liveCD it’s really useful for penetration testing purposes. If you want to install Kali, you can!
Here you can find the tools in use by Kali
If you are testing networks, always make sure you have permission to do so (if it’s not your own network ;))
Short introduction to Kali