Why is apt in the Repo?

[Chime Hart]

Hi All: I was sure surprised to be able to install apt, however, in 
/etc/apt/sources.list is empty. The man-page only seems to make references to 
Debian versions. So, inquiring minds wanna know. Right this second I don't 
remember which I used, pacman or yay? Thanks so much in advance
Chime