To explore the organization that some (very few, actually) so vehemently protest, we must first explain what Masonry IS! Here are some key points:
Freemasonry is the world's oldest and largest Fraternity. While its traditions look back to earliest history, Masonry in its current form appeared when its public events were noticed by the residents of London, England in 1717. Although Masonry - particularly in its earliest days - had some elements of secrecy, the first 'exposure' of the supposedly highly-secret Masonic ritual actually appeared in 1696! Since that time, there have been tens of thousands of books published about this 'secret organization'. And for over three hundred years, despite the good works done by its members, Freemasonry has continually suffered the slings and arrows of those who seek to use it's quiet nature against it.
Freemasonry's singular purpose is to make good men better and its bonds of friendship, compassion and brotherly love have survived even the most divisive political, military and religious conflicts through the centuries. Freemasonry is neither a forum nor a place of worship. It is not a religion nor does it teach a religious philosophy. For nearly three hundred years it has attracted men of high moral character who support the tenets of temperance, fortitude, prudence and justice.
Today, the more than four million Freemasons around the world come from virtually every occupation and profession. Within the Fraternity, however, all meet as equals. In fact, one of the most fascinating aspects of Freemasonry (and an obvious source of irritation for those who thrive on the seeds of discontent) has always been: how can so many men, from so many different walks of life, meet together in peace, ignoring political or religious debates, to conduct their affairs in harmony and friendship and to call each other "Brother!" It's truly a conundrum which perplexes those outside the fraternity. Laying aside petty jealousies and agreeing that issues of politics and religion are not proper for discussion within a lodge, the 'bones of contention' that so often divide are removed thereby making it possible for men of varying religious and political interests to meet on common ground.
Freemasons are taught to conform to the moral laws of society and to abide by the laws of the government under which they live. They are men of charity and good works and they engage in charitable works which have made them "the World's greatest philanthropy!" Their services to mankind represent an unparalleled example of the humanitarian commitment and concern of this unique and honorable Fraternity.
NOTES:
Freemasonry is not a religion, although it is religious in nature only in the fact that to join one must profess a belief in the Supreme Being or Creator of the Universe and the immortality of the soul. So Atheists cannot join. There is a long and lengthy explanation for this but I won't bore you with that now.
I assume from your avatar that you are a female. Freemasonry is a male only organization; it is a Fraternity, not a Sorority. So if in fact you are female, you will attend your Dad's Lodge as a guest for dinner, nothing more. I often bring my daughters to my Lodge for different functions and they always have a great time. Here in the US there are some girls and women's groups associated with Freemasonry that they can join if they want to. It's not Freemasonry but has the same moral instruction and fraternal/maternal feel about it.
As stated above it is not a secret society and we do have secrets. But in truth they are the modes of recognition and some passwords. Why secret? Simple really. If a man cannot be trusted to keep a simple password to himself then he has no honor and cannot be trusted with more important things. Freemasons promise never to reveal these so called secrets, but anyone can go to the library and find out for themselves. If you ask your Dad about it there is very little he cannot actually tell you. So if you were to ask him is this the password Dad? he would probably smile and say he cannot reveal that and that would be that.
To rid yourself of some of the more crazy crud you may have heard or seen on the Internet and even in on or two of the answers here {faceplam} you can go here: http://www.masonicinfo.com
Or to ask actual Freemasons some question (if your too scared to ask your Dad) go here: http://www.askafreemason.org