Idk about "most CS grads know". More like "huge Linux command line aficionados know". Although, at a certain point probably bash is terrible / for n00bs and ksh ftw or some such...
I mean, everyone with an interest in Linux should know "it's probably the config file for bash shell, the "normal" shell on a Linux terminal". If this is news to you and you are learning Linux, know that ".*rc" is a startup script / setup configuration for *. See also .vimrc (for the text editor Vim, ldo), or the system V init scripts in /etc/rc.d (system boot up) and so on. Some say it stands for "runtime config".
Imo you've gotta be fairly into it to actually know much about it though / write your own from scratch without just copy/pasting useful snippets off the internet. I've used Linux for maybe 18 years and never once messed with it lol.
like learning anything these days, just google and read / watch. man bash if you're stuck in a terminal without internet