Think of the router as two parts - a WAN interface to the DSL or Cable modem that gets and uses an IP address to the internet from your ISP.  The other part would be the internal LAN DHCP server (a limited computer server) that issues IP addresses to computers that hook up to it and in a special range of addresses reserved for internal networks and not available to the internet.  So when the two halves talk to each other to complete a transaction, Network Address Translation happens - you are (for instance) 192.168.1.2 and you click on a link.  Your browser talks to the server (192.168.1.1) and it talks to the WAN side of the router and it (lets say 216.133.124.55 for instance) talks through the modem to your ISP.  Eventually the info you requested comes to the ISP and it sends it to 216.133.124.55 for you.  The WAN side grabs it and passes it to the DHCP LAN side (192.168.1.1) and it looks in its table and because of packet ids knows it goes to your computer at 192.168.1.2.  That is wordy but explains NAT.

Firewall enhancements would be the closing of all ports but the HTML and email ports by the LAN side server, along with the control of who and what can be passed and where.

Excellent info.... answered my questions.

Thanks

User controls would be the firewall capabilities of your router - open IE or your browser of choice and put the IP address of the router in the Address box at the top and you should be prompted to log in to the router.  From there you browse to the different settings areas and pages.  The Owner's Manual will explain it all, how to move around the settings areas of the router.  As for what to set or why, that takes networking savvy and only is needed for special situations like certain games, messaging software, or setting up a VPN that need ports open.  Normal usage is to leave all closed to protect your network.  A test to see how protected you are is at:
http://www.dslreports.com/scan

Read up on these sites for more explanations and help:
www.homenethelp.com/
www.practicallynetworked.com/
www.linksys.com/edu/

All normal connectivity works between my new Insp8600 XPHome to my Dimension 8200 (XPpro) on the LAN. 2300 router works fine outbound for both computer with the laptop using wireless.

BUT, I'm trying to setup a vpn connection from the laptop (client) to the 8200 (server) via dialin. There is absolutely no documentation on how to do this on dell's site. The 'manual' states that it supports PPTP and IPSec passthru but doesn't indicate any settings etc. I've configured the 2300 router as per the below table. I've configured insp laptop and Desktop XPpro system correctly according to MS support sites (not too many options to change).

Can I access a VPN server behind the 2300 router? Is there some setting that I am missing?

BTW, your link to DSLreports run against my ipaddr  

Thank You.

Custom Port Forward Settings 
Service  Enable  Incoming Ports  Destination IP Address  Destination Port  type EDIT
PPTP         Y       1723-1723         192.168.2.2              1723-1723                 both edit
PPTP         Y       47-47                 192.168.2.2               47-47                        both edit
IKE             Y       500-500             192.168.2.2               500-500                    both edit
IPSecNAT  Y       4500-4500         192.168.2.2               4500-4500                both edit
IPSecESP  Y       50-51                 192.168.2.2               50-51                        both edit

slamalot-to congifure VPN capabilities, set the TM2300's LAN IP address as 192.168.1.1

Update any client static IPs accordingly.

keep us posted