I just read the post here. It just said.
This statement is true because there are special files that are more than just files (named pipes and sockets, for instance), but to keep things simple, saying that everything is a file is an acceptable generalization. A Linux system, just like UNIX, makes no difference between a file and a directory, since a directory is just a file containing names of other files. Programs, services, texts, images, and so forth, are all files. Input and output devices, and generally all devices, are considered to be files, according to the system.
I think I just didn't understand it enough and well. and I didn't know how to understant it. How all the things in Linux(like device, process,net connection, program etc) are treated as a file? Could anyone ptell me more about this issue?