Описание тега chardev
A character device is a custom kernel module communicating with user space in an unstructured way.
Character devices allows communication between user space and the kernel in a way that is not structured around any specific predetermined way. /dev/null, /dev/maps and the TTY are all examples of character devices.
The above is in contrast to block devices, which communicate with user space through blocks of data, usually destined to some non-volatile storage.