From Masonic Wiki
Ancient Freemasonry (also known as Antient Freemasonry or Anglo Freemasonry) is one of two main schools of thought in Freemasonry. Modern Freemasonry is the other.
Ancient Freemasonry was first referred to as such in 1751, when the Antient Grand Lodge of England split off from the Grand Lodge of England. Adherents of the original Grand Lodge after 1751 were referred to as "Moderns" even though they predated the Ancients. The two groups reunited as the United Grand Lodge of England (UGLE) in 1813.
The contemporary split between Ancients and Moderns dates to 1877, when the Grand Orient de France (GOdF) dropped a belief in God as a requirement for membership. In response to this and other factors, UGLE withdrew its amity with GOdF and declared it "irregular." The schism between the two Grand Lodges persists to this day.
In General Ancient Masonic jurisdictions are more religious in nature than their Modern counterparts and continue to require a belief in God as prerequisite for membership. Ancient Freemasonry is prevalent in most of the English-speaking world, including the United States, Canada and the United Kingdom.