Comment 6 for bug 1541678

https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin-net_id.c#L29 explains it pretty well

So there's the two letter prefixes:

"""
 * en — Ethernet
 * sl — serial line IP (slip)
 * wl — wlan
 * ww — wwan
"""

Then there's the type of names:

"""
 * Type of names:
 * b<number> — BCMA bus core number
 * c<bus_id> — CCW bus group name, without leading zeros [s390]
 * o<index>[d<dev_port>] — on-board device index number
 * s<slot>[f<function>][d<dev_port>] — hotplug slot index number
 * x<MAC> — MAC address
 * [P<domain>]p<bus>s<slot>[f<function>][d<dev_port>]
 * — PCI geographical location
 * [P<domain>]p<bus>s<slot>[f<function>][u<port>][..][c<config>][i<interface>]
 * — USB port number chain
"""