IP configuration/subnet concept problem

Hello to all (newbie here!)

I have internet access in the office that i work in. It is a single cat5 cable that plugs into the back of the PC (network card). I have configured the PCs network card with the following IP config:

IP address - 192.168.18.74
subnet mask - 255.255.255.0

gateway - 192.168.0.254

dns1 - 62.???.???.???
dns2 - 62.???.???.???


* The IP address is static. All IP config info as supplied by IT
tech.

What I would like to know is how can the IP address route packets to the gateway address, when both IP address and gateway are on different subnets??? The above IP config info works and there is internet access.

Further to this I am trying to set up a NAT router. (shared internet connection) - this is not working. This is why i ask.

Any explanation would be appreciated!

many thanks.

Your office has a at least one router with some static routes setup.
Basically, your office is divided into subnets (like your own x.x.0.x network). And there is a router setup with static routes that allow communication between the subnets.