Question : Cisco software feature set question

Hello!

I'm fairly new to Cisco. I want to download upgraded IOS, but when I tried i got the prompt below.
What is the differences between these feature sets?
Which of these make any sense for a "normal" router running NAT?
How do I find out which feature set I currently have on the router?

Select Software Feature Set:
ADVANCED ENTERPRISE SERVICES
ADVANCED IP SERVICES
ADVANCED SECURITY
ENTERPRISE BASE
ENTERPRISE SERVICES
IP
IP BASE
IP/ADSL
IP/ADSL PLUS
IP/ADSL/FW/IDS PLUS IPSEC 3DES
IP/ADSL/IPX/AT/IBM PLUS
IP/ADSL/IPX/AT/IBM/FW/IDS PLUS IPSEC 3DES
SP SERVICES

Answer : Cisco software feature set question

You may want to look at the feature navigator.

http://tools.cisco.com/ITDIT/CFN/jsp/index.jsp

Select "Search by Product Code"
In the new window, select IOS for Software
Select your platform and then click "Continue"

After a moment, the page will refresh and you can select the feature set. Then scroll down and see what features are supported by the selected feature set.

Or you can search by feature.