I want to know IP address
ifconfig from a terminal command line will tell you the internal IP address. Type ifconfig | grep "inet " | grep -v 127.0.0.1 to remove a lot of the unneeded text.
If you want your external IP address, just go to whatismyip.com or to Google and type 'IP Address' to show your public IP.
You can also find your internal IP address by going to System Preferences | Network and viewing your current connection (either AirPort for wireless, or Ethernet for wired, typically). Your status should display the current IP address.