Yes, you NEED the entry for the loopback interface in there.. (lo)
do as repo suggested and uncomment those two lines in the interfaces file
# The loopback network interface
iface lo inet loopback
iface eth0 inet static
I guess I wasn't specific enough and should have said to ONLY edit the eth0 portion.. you did say you were new
Sorry bout that..
At least the rest of your networking is functional now.