411 is Directory information. If you call that number you can give them a person's name and they will give you their number (land line not cell service) If you call 911 however, even if you hang up, the police will come and check on you, If you call them on accident, always stay on the line and let them know it was an accidental call.
4-1-1 is local directory assistance in U.S and Canada. When you call the number, they are able to assist you in finding details of a person including their contact information. However, that service has been discontinued in most of the places.