Parameters

Devices: -i, -o
Input/Output interface (e.g. eth0, ppp0)
Input chain only has input
Output chain only has output
Forward chain has both
ppp+ will match all interfaces beginning with 'ppp'

Source/Destination: -s, -d
name (www.kernel.org)
ip (192.168.0.1)
network (192.168.0.0/24)