A.F. & A.M. means “Ancient Free & Accepted Masons”.
The term Ancient originated in England during the Middle Ages. After the foundation of the first Grand Lodge in England in 1717, a rival Grand Lodge arose less than two decades later, calling itself the Antients (or Ancients). The Antients were also known as the Athol Masons, from their first Grand Master, the Duke of Athol.

Why Free and Accepted?
The ancient craftsmen were very skilled, and their craft was considered to be indispensable to the welfare of both church and state. For this reason, they were not placed under the same restrictions of other workers – they were “free” to do their work, travel and live their lives in a manner which befitted their importance.
In Medieval England, this freedom of movement was almost unheard. Most workers were under bond to the owners of the land on which they worked. We believe this freedom for the operative mason may date back as far as the year 946 in York, England.

During the latter years of the Middle ages, there were few educated men outside the monasteries of the church. Naturally, men wanted to become Freemasons to get the advantages the Craft had to offer. These men did not necessarily want to build buildings, they wanted to belong to the organization.
These were “accepted” Masons rather than operative masons. This practice probably originated when some of the people for whom craftsmen were working asked to be admitted and the practice grew with time. This was a big boost to Masonry, because the secret techniques of building trades were becoming more widely known.