X11 / Xorg / XFree modules documentation

It is possible to load many modules using xorg.conf, for example:

Section "Module"
	Load	"i2c"
	Load	"bitmap"
	Load	"ddc"
	Load	"dri"
	Load	"extmod"
	Load	"freetype"
	Load	"glx"
	Load	"int10"
	Load	"type1"
	Load	"vbe"
EndSection

Is there some online/ps/pdf documentation about each of these modules?

For example ${THIS} modules is needed to achieve that and that and provides extensions for that and that ...

Is something like that exists?

If not please put here links that provide other X11 / Xorg / XFree documentation.

Thanks in advance.

These forums are text/console focused and graphical modes/interfaces are rarely discussed here, is that is why I got no response?

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