Apologies for the off topic Linux noob post.
I have dabbled with a Raspberry Pi, just following instructions really, so I have used sudo apt install xyz.  When you put in the application name, like get-iplayer, how does "it" know where to find the software?

(As a user for many, many years, thanks very much to DinkyPumpkin et al for all the fantastic work keeping GiP alive for the community).