Predictable Network Interface Names
( https://raspberrypi.stackexchange.com/questions/37920/how-do-i-set-up-networking-wifi-static-ip-address/37921#37921 )

Stretch introduced1 predictable network interface names which have been used in other distributions for some time.

Network interfaces will have names formed from a prefix en — Ethernet or wl — wlan followed by x indicating MAC and the MAC e.g. enxb827eb123456 or wlx00c140123456. The onboard WiFi of the Pi4, Pi3 and PIZeroW which is connected over sdio will however use the name wlan0

This can be beneficial to those using multiple network interfaces, however for most Pi users, with a single Ethernet and WiFi interface will make little difference. The previous names eth0 and wlan0 can be restored if you pass net.ifnames=0 on the kernel command line in /boot/cmdline.txt.

There is an option in raspi-config to enable predictable network interface names.