It's a bit more complicated than that.
If you are talking about IPv4, then in most cases ISP will assign you one IP (static or dynamic), and you wouuld use routing to share your connection between several terminals.
in that scenario entire local network would be seen from internet as on device and inside LAN you would use internal-only adresses (like 192.168.xxx.xxx).
your ISP can provide you with several IP's, and then you can assign external addresses to speciffic machines in your LAN and in that case every computer with assigned external address would be directly accessable from internet.
last scenario is when your ISP gives you IPv6: you would usually get a subnet (range of addresses, and then every computer you hook up to your router will have it's own IP and will be seen from outside.
Last edited by patryk; 03-21-2013 at 12:44 PM..