[gentoo-user] Without udev, who/what names ethernet devices?

[Chris Stankevitz <chrisstankevitz@gmail.com>]

Hello,

A USB serial device is identified by the characters "/dev/ttyUSB0".
One might call this string a "device on your filesystem" and it can be
opened/closed just like any other entry in the filesystem.

An ethernet device is sometimes represented by the string "eth0".
Regarding this string "eth0":

1. What does this string represent?  Is it a file on a filesystem?
(no!)  Is it okay for me to call it an "ethernet *device*"

2. Assuming udev is not running, who/what comes up with the name
"eth0"?  How does that person/thing know how many ethernet devices
there are and in what order to enumerate them?  What happens if
ethernet devices are dynamically added (e.g. a USB ethernet device or
a driver being loaded/unloaded)?

3. How does (2) change when udev is running?

Thank you,

Chris