how do I get my "external IP address"?

I am trying to find out my external IP address. Also I probably have a few misconceptions as to how ISPs and IP addresses work. First of all I connect to my ISP with DHCP. Currently when I check my IP address I see that my IP address is 10.200.18.159. This is a private IP address. These addresses are private and not accessible from the internet from my understanding:

(10.*.*.*)
(172.16.*.*) through (172.31.*.*)
(192.168.*.*) through (192.168.255.255)

So this means that my IP (10.200.18.159) is an address on my ISPs private lan.

My major question is this: do I have an "public IP address" also? In other words; if I were to go to a different machine, outside of my home network, could I type in an IP address into a web browser and reach that machine (assuming I have a web server running)? I tried this one site that claimed it could tell me my address:

http://checkip.dyndns.org:8245/

and it returned:

http://216.157.205.249/

that dirrected me to a site that sells routers:

www.MikroTik.com

I guess the strange thing is that if I run a traceroute to any site I get this for the first few addresses:

1) 10.200.18.1 (I am assuming a gateway or proxy of my ISP)
2) 216.157.205.250 (the mikrotik website)
3) 10.200.1.1 (I am assuming a gateway or proxy of my ISP)
4) 63.89.180.254 (no idea)
5) 64.186.46.5 (no idea)

Is this maybe some technique that they use to mask my "external IP" address from me? Am I misled in believing that there is such a thing as an "external IP address"? I don't know all the inner workings of TCP/IP. But I am assuming that there is not a persistent connection. In other words; a client sends a request for a web page. The ISP does name resolution using a DNS server and forwards the request to the server that has the page. Does the web site then send out the page with the clients IP address (in which case the client would have to have an IP address that is accessible from the internet)? Or does the server simply return it to the ISP and the ISP handles getting it back to the client?

The way I find my IP is by opening a command box (Start > Run > "command" > enter)

Then type ipconfig

Hope that was what you wanted.

Try this site..

http://www.showmyip.com/

EDIT: Sorry, I didn't see that you had already found "http://checkip.dyndns.org:8245/ ".

That should give the same address.