How can I check someone IP address ?

I want check someone IP address so tell me that is this possible and if yes then tell me how ?, Plz help me in this ! it necessary for me !!!

Checking someone's IP depends upon the method you are using. If you want to check your IP then simply open whatismyip.com website and it will show your IP. But if you want to know the IP of person you are chatting on facebook then you can't do that unless you are an hacker and can heck into facebook and then findout the IP of the person.. .. ofcourse I am joking.