That is true. Provided the operating system you are trying to boot is built for the processor you have in your laptop. You cannot boot an Intel laptop into Raspian which is an ARM operating system.
But from a beginner user's point of view, the difference between Debian and Raspbian (or Fedora and Pidora, etc...) should be more or less academic (apart from the performance, which is basically just the hardware difference anyway, and a few nice installation / config scripts etc.)
What we're trying to get at is: You can't use the same OS image on a 'normal' i386/amd64 PC and a Raspberry Pi. But Raspberry Pi versions of Linux distros are basically just normal Linux distros recompiled for the ARM chip with a few extra goodies - almost everything you learn on one system is directly transferable to the other.
(Granted, you won't be able to download random binary .debs you've found on the net and get them to run on the Pi. But you probably should be sticking to the main repositories anyway as a beginner, at least with Debian. The Pi Store is a bit of a wild-card, but there isn't much in it yet I don't believe...)