Hello all,
I have been using Linux for quite a while but there is one thing that I have never fully understood, and that concerns the Linux kernel. Here are the questions that I have.

1. The first question that comes to mind is why are there so many of them? There are the 2.4 series and then the 2.6 with many different ones included in each series.

2. Why do so many of the distros have their own custom kernel?

3. If you are using a distro that uses a custom kernel could you download and use one of the vanilla kernels? Or would this break your system?

4. If using one of the vanilla kernels would be safe to use which one should you choose? Or should you stick with the custom kernel the distro provides?

Thanks for any insight that you might be able to give me.