I am new to linux and after looking for a suitable distribution to start learning, I have decided to use knoppix installed in my HD.
Looking at different distributions, I know that the linux kernel is common to everyone, but depending of the distro,
That is correct.

I think there are certain konsole commands that are particular to each version, for example "apt-get" for Debian, "emerge" for Gentoo and so on.
Debian's apt-get/dpkg and Gentoo's emerge are high level software package managment tools & yes they are specific to a particular breed of linux distros. Something to remember is that apt-get is NOT specific to just Debian or Debian based distros like Knoppix or Mepis. Apt-get/synaptic is a front-end to Debian's dpkg system. As a front end, it can and is used on RPM based distros like redhat & suse.

but is there anywhere specific information about Knoppix (Debian) thant explains well the particularities of these distros???
I gather that you are looking for more info on Debian package management. Here is a Apt HOWTO http://www.debian.org/doc/manuals/ap.../index.en.htmland FAQs on Debian package management http://www.debian.org/doc/FAQ/ch-pkgtools.en.html.

If you are looking for books about Knoppix:
NewsForge | Review: "Knoppix Hacks" - I wrote this review. The author, Kyle Rankin, also posts on this forum. Great book for experienced people or people not afraid to experiment.

"Moving to Linux: Kiss the Blue Screen of Death Goodbye!" - Even though I am not a newbie (I'm a Unix & Linux sysadmin), I bought this book. Great for newbies.

As for 64 bit Debian, Knoppix based KANOTIX has a 64bit LiveCD available.

I hope this helps.
James