IPs and Networks.

Hey guys. I'm trying to understand everything about Metasploit. But there's just some things that kind of confuse me and I'm hoping you guys can solve these problems. I understand how networks and IP's work but....

1. how could you find your "target" on a LAN or MAN? (If you know there ip)

And if there on another network, how can I identify what network they're on? I understand pivoting but I don't understand how I could identify the network there on so I may get on it as well to exploit them

2. is it possible to exploit a smartphones vulnerabilities like you would a computer system?

3. how could you find a smart phone's IP? Would you need to track down there router and access the vulnerabilities from there??

Thanks guys!