What exactly happens when you type apt install?

Question

linux

What exactly happens after typing apt install "package"? how the requested package is searched, etc.

Answer 1

the package is searched in the downloaded repository listings (updated by apt update).
the cache is in /var/lib/apt/lists.
from all matching entries, the entry with the highest Version value is selected
from this entry, a link to the package is taken and downloaded.
after which the package is passed to dpkg for installation.

Answer 2

man strace
is already "chewing at a lower level" of what exactly is happening, is that what
you wanted to know?
if you don't need "system jungle", then the answer above will satisfy you :)