This file controls the configuration of the module auto-loading of system initialization. This is the file where you should explicitly specify any modules you want loaded at system startup, not /etc/modprobe.d.
The syntax of this file is as follows:
<module> [<arg1> <arg2> ...]
Each module should be on its own line, and any options that you want passed to the module should follow it. The argument deliminator is either a space or a tab. The line deliminator is a newline.
This is the directory containing the modprobe configuration files. Documentation on how to use this directory can be found at http://man7.org/linux/man-pages/man5/modprobe.d.5.html.