Router/Hub/Switch - a device to allow multiple computers to connect to each other, and/or to the internet. (well, i suppose one could configure a router to not allow inter-LAN connections, but why?) a router has "intelligence" that will allow one to configure who can talk to which; a hub is just a dumb connection that shares the bandwidth of the hub amongst the LAN; a switch allows all connected to it to use the full bandwidth. NAT - (Network Address Translation) - if there is more than one computer behind the router/hub/switch, they will each have a private "internet protocol" address (IP address). typically, the router will have an IP address supplied by your ISP. this is the only one that should hit the internet. NAT will tag each packet coming from each machine and then translate the address that it came from on it's way out to the internet. when the response comes in, it will be translated back to the address of the machine it came from. DHCP (Dynamic Host Control Protocol) - there is a fairly large block of IP addresses available, but due to the way they were handed out when the internet was the arpanet, there is a lot of waste. with the growing popularity of the internet, and all the machines that are wanting to connect to it, there is a shortage of distinct IP addresses (and each machine must have a unique address). ISPs have a range of IP addresses assigned to them. rather than assigning an address to a customer all the time, they only assign an address when that machine connects to the ISP. when that machine logs off, that address goes back into the pool to be used by another machine. hence, a "dynamic" address - one that changes. Static IP addressing - there are a few blocks of IP addresses that are not supposed to be seen on the internet. these addresses can be used at will by anybody within their home networks. (i forgot which they were off the top of my head and found the following while hunting them up.) "What Are Private And Public IP Addresses? A computer on the Internet is identified by its IP address. In order to avoid address conflicts, IP addresses are publicly registered with the Network Information Centre (NIC). Computers on private TCP/IP LANs however do not need public addresses, since they do not need to be accessed by the public. For this reason, the NIC has reserved certain addresses that will never be registered publicly. These are known as private IP addresses, and are found in the following ranges: From 10.0.0.0 to 10.255.255.255 From 172.16.0.0 to 172.31.255.255 From 192.168.0.0 to 192.168.255.255 "