Help static ip on wifi setup - Raspberry Pi

[Colbaker]

Hi all,

I am new to Linux and am using Raspian on my Raspberry Pi2, i want to set it up with a static ip so i sudo nano /etc/network/interfaces and get..

auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet manual

auto wlan0
allow-hotplug wlan0
iface wlan0 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

auto wlan1
allow-hotplug wlan1
iface wlan1 inet manual
wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

~
~
~
~
~
~
"/etc/network/interfaces" 17 lines, 295 characters

My questions are..

1. why is there Wlan0 and Wlan1?
2. how do i edit /etc/network/interfaces to add a static ip address, its a wireless router with wpa2 encryption.

Thanks all