A filesystem is a logical division within a physical partition.
As discussed during our installation chapter, we know that we have installed MS Windows and Linux on the same hard drive, however they are loaded in two separate disk partitions (physical divisions).
There can only be one of the physical partitions active at any one time, this will be the partition that you boot up with by default when the machine is switched on.
Within the Linux division we can have further divisions or filesystems based on the following decision criteria:
Size of hard drive