Difference between Kali Linux and Ubantu

[siecdubai]

I was asked by my manager to install Linux operating systems on office computers due to security reasons. I actually have no idea about it as I never used Linux. While searching over internet I came across two linux - Ubuntu and Kali Linux. Can anyone explain the difference and which one should I install? Also, where to download it?

Thanks

[karim spinxo]

Apt update