Throughout means that it continues during the entirety of the subject or time indicated, usually persistently or without interruption.
Through is more general, and doesn't imply that the action or occurance happens over and over again or continuously.
Simply, throughout emphasizes what happens, and through is more general and not continual, focuses more on the passage of time that what happens in it.
I had many visitors throughout the day.
I went through the day without many interruptions.
Throughout time there have been many wars.
Through the years I have made many friends.