What does the Makefile mean?

Http://bbs.chinaunix.net/thread-1916415-1-1.html

In the top makefile of Linux source code, there is a sentence

$ (filter-out _all Sub-make $ (CURDIR)/makefile, $ (makecmdgoals)) _all:sub-make
$ (Q) @:
What do you mean, ask a lot of people, documention inside?

It's usually used to turn off the echo of the command. If the Q value is @, then the command part is @@:, does not echo If q has no value, the command part is @:, not echo So, test to see if it can:) $ (filter-out _all Sub-make $ (CURDIR)/makefile, $ (makecmdgoals)) _all:sub-make $ (Q) @: In fact, nothing to does here.

What does the Makefile mean?