Debian vs. Ubuntu vs Kubuntu
So, I'm trying to understand the difference between pure Debian, Ubuntu and Kubuntu.
Now, I know that Ubuntu and Kubuntu are basically built on Debian, but what are the major differences? Are they less reliable/customizable? Why would one prefer pure Debian over Ubuntu/Kubuntu?
And is there any major difference in terms of performance or reliability between Ubuntu and Kubuntu? Why would you prefer one over the other, other than desktop environment preference?
The way I see it, and it's my completely unprofessional pure gut feeling, is that Debian is the more reliable and professional OS, whereas Ubuntu and Kubuntu are there just for beginners who want to play around with Linux.
Again, I completely don't know what I'm talking about which is why I'm asking, so how far is my gut feeling from the truth?
Also, is Ubuntu server a serious enough server OS?
Thanks in advance!