Everything works fine I just want to know why would my interface change to wlp2s0 by default instead of the usual wlan0
A new naming scheme has been introduced, to solve problems that arose from the old (eth0, wlan0) naming standards.
Here is a short introduction and explanation of the concept: http://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/
Basically, the first two letter describe the type of interface. 'wl' for wlan, 'en' for ethernet. The following code is often a description of the physical placement of the device in your computer - p2 is likely PCI bus 2, and s0 is likely slot 0.
As kyodake pointed out, this new standard was introduced when Ubuntu moved to systemd.
Why Ubuntu with systemd have added native support for a number of different naming policies into systemd/udevd proper and made a scheme similar to biosdevname's the default. The following different naming schemes for network interfaces are now supported by udev natively:
(1) Names incorporating Firmware/BIOS provided index numbers for on-board devices (example: eno1) (2) Names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (example: ens1) (3) Names incorporating physical/geographical location of the connector of the hardware (example: enp2s0) (4) Names incorporating the interfaces's MAC address (example: enx78e7d1ea46da) (5) Classic, unpredictable kernel-native ethX naming (example: eth0)
By default, systemd will now name interfaces following policy:
(1) if that information from the firmware is applicable and available, falling back to: (2) if that information from the firmware is applicable and available, falling back to: (3) if applicable, falling back to: (5) in all other cases. Policy (4) is not used by default, but is available if the user chooses so.