Issue about IP sniffing and Ip tacking

Question

Hi EveryBody:

Is it true that when I want to sniff a certine IP from my machine that I 
have to be apart of network, and If some security Devices such as Firewall 
and routers if them configuered well they will protect me from sniffing the 
ip?

Also What is the Diffreance betwen sniffing IP an Tracking the IP ?

any help or redirection will be appreciated

regard's

HUsam