I've always thought arranged marriages were like everyone else has said ... two families basically decide who their son/daughter is going to marry.
The movie "Bend it Like Beckham" kind of illustrates that idea because the family portrayed in that movie is from India.
Another example of an arranged marriage is kind of like how "back in the day" the King and Queen of ABC country would make a contract with another King & Queen and basically say their children will marry each other.
The second part to the arranged marriages question does sound more like a blind date than anything.