"Semper Reformanda." The church must "always be reformed."
If we asked any person on the street what the church is, we'd probably get a variety of answers. However, I'm sure many of them would give a few stock answers: the church is a building, the church is people gathered to worship, etc. None of these are wrong, but they show us how much we take these things for granted.
This is why the Protestant Reformation matters. The Reformation was about the resurgence of the gospel and thereby the true church. The church is not just a club or way of gaining social capital. The Reformers taught that the church was marked by just a few things. Some had just one mark, some had two, and some had three. I'm persuaded that we need all three to be a biblically based portion of the body of Christ.
The three marks of the church are: 1) the Word rightly preached; 2) the ordinances rightly administered; 3) and a rightly ordered community.
The Reformers were reacting to the general lack of these things within the medieval Roman Catholic church. There were of course true Christians and even true congregations with the medieval Catholic church, but the general course of Rome was that of rejection of the authority of Scripture for the authority of one bishop, the Pope—the bishop of Rome. This opened the door for a variety of abuses all stemming from misplaced authority. If a man has the final authority, the natural course of things will be to focus on an institution and hierarchy (though they are not evils in and of themselves). If Scripture has the final authority, the natural course of things will be the gospel and the things of God.
As you and your family does whatever it is you do on Halloween, take a minute and give thanks to God for acting in the Reformation. The gospel was once again made the reason the church existed. Because of this, the church must always be reformed. The gospel must never lose its rightful place in the pulpit, the classroom, and most importantly, the heart and mind of every believer.