I know that with a GNU/Linux distribution you can switch between different distributions at runtime when they use the same kernel or the kernel is compatible between 2 or more different distributions; I never used this feature of the Linux-based OSs, but I would like to ask what is the software/s that makes this possible and how to perform this switch at runtime correctly.
It will be nice to also have a list of pros and cons, for example what settings I loose and what I can keep during the switch.