What types of devices fall under the major device number category and what types of devices fall under the minor device number category. What is the real difference between the two categories?
All devices have a
major, minor number pair. The
major number is a larger, more generic category (e.g. hard disks, input/output devices etc...) while the
minor number is more specific (i.e. tells what bus the device is connected to).
Check the kernel documentation for more examples.
The major device number identifies the driver (e.g. IDE disk drive, floppy disk, parallel port, serial port, ...) and the minor number identifies the specific device (i.e., the first floppy would have minor 0, the second would be 1, ...).
Maybe you are interested on the LANANA device list: http://www.lanana.org/docs/device-list/ that descrives the major codes.
As @Renan says, minor depends on the device.