Apple ipod

What is the difference between the iPhone and iTouch? "I can install Yahoo Messenger on your iPhone or iTouch?

I am torn between buying an iPhone or iTouch. What is the difference between the two? I mean, except the phone and SMS capabilities of the iPhone? and I really want to know if I can install Yahoo Messenger on both? Thanks! Thank you all for your answers! I have another question about the iPhone, I read a review if you delete a message that can not be removed one by one if you want to delete a message, you must delete all conversations with some person.is this true? I just want to clarify this because if this is true, this would be the biggest decline of this.pls specify. Thanks in advance!

The iPhone can communicate on GPRS / EDGE (as provided by cellular carriers such as AT & T). The iTouch WiFi calls, so it's not as mobile.

Pidgin – Free Instant Messenger: AIM, YIM, MSN, IRC, GMail..