purpose of "/usr/lib/modules-load.d" & "/usr/lib/modprobe.d" ?

[Frantisek Hanzlik]

Ed Greshko wrote:
> On 07/21/2012 09:26 PM, Frantisek Hanzlik wrote:
>> Sorry, "modules-load.d" has man page. But what "/usr/lib/modprobe.d"?
> 
> man 5 modprobe.d

Yes, I read this, but can't make head of it. Shall I take it that, as all
there mentioned directories:

/usr/lib/modprobe.d/
/etc/modprobe.d/
/run/modprobe.d/

are quite equivalent? When yes - we had there for long time
"/etc/modprobe.conf" and "/etc/modprobe.d/", thus why are there another two
directories?