There area a zillion manufactures of M-1 Carbines. You can get a book that'll explain them, or maybe the net will outline all of the makers.
They made 5 millionn of them in WWII. They made more carbines than they made Garands. The WWII guns don't have a bayonette attachment, many were retrofitted during the Korean War.
They can be pretty tempermental. Mine stove pipes from time to time, but they are easy to clear, not like an AR-15/M16 with their bolt override problem.
Mine is pretty beat up, was a guard gun at San Quentin prison, so while it's got handling ware its bore is like new and they thing shoots very good indeed.
Most military ammo that I've found is Korean stuff and it's good. You can buy after market ammo too that's cheap. Mine doesn't have the bayonette mount and that's as I like it, as it's like the WWII model.
Old ones have a "L" shaped rear sight that had only two settings, you "flipped it over". But before the war was over they mounted an adjustable peep sight.
The only stuff I have on mine is a sling, that mounts through an oiler in the butt and a magazine pouch that fits over the wrist of the stock. Many of the magazine punches that you see don't mount on the rifle, rather they are made for the belt. The rifle mounting ones are getting kind of expensive as they make the gun "neater".
You can find after market folding stocks, but I don't know why you'd want one. If you find an original folding stock carbine you are talking about pretty big money.
They carry and mount almost exactly like a Ruger 10/22. I'm sure the Bill Ruger was trying to duplicate the feel of the carbine when he made his little .22 auto.
It's easy to get parts for them. Don't buy the Universal one that was made about 15/20 years ago. They might work okay, but they don't have the charactor of the old one. Also some Universal guns have a real ugly steal upper forarm.
They used to be cheap, but no longer. I think minty ones go for $600 plus at gun shows, older, beat up ones cheaper though.
Anyway, I like mine, they are easy to carry, fun to field strip, ammo is cheap and they are just neat little shooters.
They are also part of history.
BTW: An old Marine friend of mine told me that he shot a Jap Marine 13 times in the chest while fighting on Siapan. He said the guy keep coming. After that episode he tossed the carbine and picked up a Garand. They hit lots harder. The 30 Cal short round is about like a 3220.
