Ethernet Sheild - Read/ Write

Can you read and write to the Arduino board when you have an Ethernet shield? Say I wanted to turn on three leds. Could I do that with the Ethernet shield, using Ethernet. Sorry if it is a confusing question but I can't seem to find the information anywhere.

You can, but you need to find out, what pins are used by ethernet shield. Now there's a place for learning important things. Every shield use some I/O pins, you need to figure, what which are left for having fun.

Go to arduino's main site, and start from "Hardware" section.

Now, some spoon feeding; http://arduino.cc/en/Main/ArduinoEthernetShield

Cheers, Kari