A firewall is a "layer" provided by specialized software. It functions as though it is sitting "between" the local-area network of a company and the internet. It is constructed to allow the administrator of the local network to limit what kind of traffic is allowed to pass through into the LAN, what (for example) IP numbers are allowed to be addressed, what kind of streams of data are allowed to come in and to where, and in some case which sources are allowed to send queries or data intot he local network. The term comes from the word used in both automonbile and steamship construction for the physical wall separating the engine area or the boiler area from other compartments (such as the driver's cockpit in a car, or perhaps holds or tanks in a ship). The firewall was often lined with asbestos sheeting to prevent the "hot area" from heating up the adjacent compartment.

The analogy is that the uncontrolled internet is "hot" while the other side of the connection -- for example an office LAN -- has to stay controlled and "cool".

IP stands for Internet Protocol, and an IP number is the xxx.ttt.zzz formed number which is assigned to any operating "node" on a network using the "TCP/IP" (Transfer Control Protocol/Internet Protocol) method of communication and networking. When you log on to the internet your machine usually has an IP number, and it is either a constant number every time you log on (static IP) or it is an IP number assigned for the purpose of that session only, then to expire and be reused somewhere else (dynamic IP).

For a semi-technical explanation click on this link.Regards,

Amos