Master Mason and Past Master of a Massachusetts Lodge here.

I can't speak to the American Revolution nor the origins of Freemasonry authoritatively (I am not a historian, and the origins of the fraternity are somewhat hazy. Freemasonry as we now know it began with the establishment of the United Grand Lodge of England in London in 1717, but evidence such as the Halliwell Manuscript suggests that Masonry had been already existed in some form for hundreds of years.)

The Freemasons are a fraternal order that uses the tools and implements of actual stone masons as symbols to illustrate moral principles. It is not a religion, but does require candidates to affirm a non-specified belief in a supreme being. It also makes no distinctions of social or economic class - which means that men of all faiths and walks of life may sit together as equals in a lodge. Modern lodges do not get involved in politics; one of the first things that is (or should be) deeply impressed on every new member is that religion and politics are not to be discussed in lodge.

The Masons are still around, and have changed somewhat with the times, although in Massachusetts the basic process and ceremonies of initiation have not changed much in a very long time. Like most other fraternal organizations the Masons struggle to attract members because they have to compete with television and other modern distractions, long commutes, and more hectic schedules in families where both parents work and kids have multiple extracurricular schedules. In the US many lodges have gotten themselves into tough situations by failing to raise dues to keep up with inflation since the 1950s-60s. But, much depends on what country and/or state you're in; there is no single global Masonic organization; each country has its own Grand Lodge, and in the United States each state has its own Grand Lodge and while Grand Lodges do maintain relationships with each other, they all do things a little bit differently. And within any given Grand Lodge's jurisdiction, each local lodge has its own little traditions and overall flavor.

Recommended reading: Freemasons for Dummies (no, really. It's a solid and straightforward overview of what Freemasonry is about and goes into more detail on the different theories about the origins of the Fraternity) and Solomon's Builders - Freemasons, founding fathers and the secrets of Washington, D.C. by Christopher Hodapp (published in the hype leading up to Dan Brown's "The Lost Symbol", but duly researched and not as sensational as the title might suggest) and The Better Angels of Our Nature - a fascinating and well-researched book about Freemasonry on both sides of the American Civil War.