Can't remember exactly = Assault Rifle or Automatic Rifle.
Armalite (a division of Fairchild industries, maker of the wonderful A-10 Warthog) had the design from Stoner and later sold it to Colt.
Colt originally made the weapon for the US military, as did divisions of GM (my first M-16 was a Hydramatic). But, patents run out.
Now, the design is a "pattern gun" made by nearly everybody.
But, the top three are ABC:
Armalite
Bushmaster (highest civilian sales)
Colt
Many others (Rock River Arms, Wilson, Knights, et al) are also making the same rifle, but with much lower sales. Knights makes the high-end, specialized versions costing big $$$. Parts are very standardized and interchangeable.
FN currently makes the M-16 (M-16A2 and M-16A4) series under contract.
Colt makes the M-4 under contract, because they exclusively own the TDP (Technical Data Package) for the M-4.
Of the manufacturers of AR 15, how do they rank in quality?