What exactly is it that the different distributions add?
Do they make any modifications to the kernel?
Do they write their own device drivers?
How can there be a specific Red Hat hardware list?

Thanks

> What exactly is it that the different distributions add?
That would take a novel and a half to say "exactly". Most or all distros have the core utilities, and most have things like Mozilla, Open Office, and various window managers.....then it's up to the developers to decide what other 3rd-party stuff to add.

> Do they make any modifications to the kernel?
Yes. This is one of the reasons I tend to stick with SuSE. Take v9 for example....the kernel is listed as 2.4.21-99, but they took some useful features from the development 2.6 kernel and added it into the default 2.4.

> Do they write their own device drivers?
I really have no idea.

> How can there be a specific Red Hat hardware list?
RedHat is looked upon by many as being the "standard" Linux, so a lot of developers will use this distribution as a testing ground for drivers and other software. There's really no RedHat-specific software, but some software which installs and runs easily in RH (because it was built against it) may be troublesome or more difficult to get working in another distro.

The main difference is in management, packaged applications, and what patches or modifications are made to the included packages.

BTW: The modifications may claim better hardware support, distribution value adds, bug fixes, etc...

It is my opinion that the most important aspects of a distribution are: management (future plans, agendas, survival models), and standardization (both LSB, file system, and administration methods).

I can't help myself to not plug a new community maintained RPM based distro here:
http://www.linuxquestions.org/questi...?s=&forumid=44 (cAos)