HEMA stands for Historical European Martial Arts.
Thankfully for us, from roughly the 1400s, certain masters and practitioners began to record their art, either in verse, or in writing, and sometimes with images as well. The earliest source we have is the Royal Armouries Ms. I.33 (circa. 1300) which deals with sword and buckler. The sources extend all the way through the ages until we come to 19th century sport and military fencing, and up until the present day.
There are treatises and books about fencing with many different weapons - spear, staff, mounted combat, armored combat, the longsword, sabre, rapier & dagger, sidesword, messers, dussacks, daggers, wrestling.
HEMA today recreates and reconstructs the martial arts of old, and for those that wish, sporting events are held, similar to modern fencing tournaments. There are no set rules, and no "masters" per se. The scope of practice is vast. Some treatises are a holistic system, some concentrate on a specific weapon.