Most humans use a GUI when they can(with their connections stored and autocomplete and a few other nice-ities. Of course if you only ever use MySql or Postgres through command line, congrats - you know how to do basic connections(I assume using -h makes you an imposter)
As for the Linux/tar piece, I've used Linux on desktop for a few years(both Ubuntu & Fedora) & have used Suse and CentOS for servers for much longer.
I can tell you tar means tape archive. I can tell you I mostly use it with gunzip to compress it. I still google/reverse terminal search what flags to use with it both when archiving it and unarchiving it. I could probably remember some flags if I spent enough time thinking - why would my brain waste that much effort though?
I don't work as a backup administrator. I have better things to worry about knowing/having present at the forefront of my (admittedly human sized) memory.