FA meaning in Military and Defence ?

Field artillery is a category of mobile artillery used to support armies in the field. These weapons are specialized for mobility, tactical proficiency, short range, long range, and extremely long range target engagement.

Until the early 20th century, field artillery were also known as foot artillery, for while the guns were pulled by beasts of burden (often horses), the gun crews would usually march on foot, thus providing fire support mainly to the infantry. This was in contrast to horse artillery, whose emphasis on speed while supporting cavalry units necessitated lighter guns and crews riding on horseback.

Whereas horse artillery has been superseded by self-propelled artillery, field artillery has survived to this day both in name and mission, albeit with motor vehicles towing the guns (this towed artillery arrangement is often called mobile artillery), carrying the crews and transporting the ammunition. Modern artillery has also advanced to rapidly deployable wheeled and tracked vehicles and precision delivered munitions capable of striking targets at ranges between 15 and 300 kilometers.