Can anyone tell me the difference between apt-get and yum

which one is better and why?

I am running fedora core 2, installed apt-get but it seems like it's not working for some reason, yum works just fine.

There isn't a whole lot of difference between the two, from the view of a user. Both do the same things. Both have similar configs. As long as both are pointed to repositories with the same packages, you will end up with the same packages updated from either.

I s'pose choosing one over the other would depend on what repos you want to use. If you want to use a repo that only supplies apt, then use apt. If not, I haven't found a reason yet to not use yum.

The only annoyance I have so-far with yum is that it checks the repos for new packages for everything it does. With apt, it would only check the repo when you told it "apt-get update". Of course, it might just be me... I used to use apt on RH9. Since I've been running Fedora, I've been using yum.

so what you're saying is that yum support both apt & yum repos? if that's the case, that's pretty cool.
So in Yum/apt-get, how do I change repos? Can they use more than one repos so it finds everything? There are things I couldn't find on them, such as fluxbox, ccm and things like that.

apt was built for debian and almost all versions have a gui, it also works for most platforms were as yum was made for rpms to solve dependancys but most versions don't have a gui

Not quite... Most repos only support yum or apt. Some few might support both... It depends on the maintainer of the repo.

You can change repos by editting the conf file of either program. /etc/yum.conf or /etc/apt/sources.list or /etc/apt/sources.list.d/* . You can point either to a number of different repos. If you point to a number of different third-party repos, you might run into a bit of trouble if they contain different versions of the same packages.

I know in yum, you can point to different mirrors of the same repo... When running yum, it tries the first server. If it can't reach it, it rolls over to the subsequent mirrors. Take a look at << www.fedora.us >> for a list of mirrors.