"initrd" is rather a bit of a hack...
"A hack" is rather like 'a particularly elegant archway over the front entrance to a supermarket.'
It perfectly-satisfies the particular need that it was designed for, but you might prefer not to admit to having been the person who actually designed it...
The problem that the designers of Linux (distributions...) had to face is, "how can we manage for our operating-system to successfully boot itself ... one way or the other ... on 'any
old-or-new piece of computer-junk on this planet?'"
You see, every "piece of computer-junk" (yours and
mine...) consists of a peculiar set of hardware-devices, each one of which requires its own peculiar set of software-drivers. Therefore, in order to "not only 'work,' but 'work gracefully'
," Linux needs to have some way to identify the hardware and load the proper set of drivers "on the fly!"
Once Linux has accomplished that,
it can proceed to "boot normally."
In short, "that's what initrd
does." And, yeah, "it's magic." Serious
(This is also what gives you that nice, reassuring, graphic logon-screen that presents a nice splash-image and a progress bar that all but screams to you, "pay no attention to the little man behind the curtain...")
So... "I'm sorry to have spoiled 'the trick.' But, this is how 'the magic' is actually done." Now you know. Windows does it, OS/X does it, and Linux does it...