Basically a muzzleloader is a gun you load through the muzzle, ()add powder and a bullet manually,
not a loaded case and bullet like a cartridge is loaded into an action on a rifle or shotgun!
think of basically black powder rifles and pistols, of either flintlock designs, or more modern inline designs
many states consider each in a class of its own, meaning they can have special rules and regulations on when what type of muzzleloader can be used, many also have rules regarding what the legal sights can be, some require ONLY open sights, some allow more modern sights, like scopes and such! some seasons are also called other names like primitive weapons only, some are called flink lock seasons, , some Muzzleloader seasons, and so on!
details matter and its also why folks need to read rule books well and understand things, and if have question ask, and find out, but as always, some times the BEST info, can ONLY come from the state game dept you are in, as folks on forums such as this can give bad info at times, even when they MEAN to give GOOD info, so taking teh word of a stranger on a forum, is not always the best way to find answers to game regulations where you are at and where you plan to hunt, far too many small details and rules in states, zones, and likes for anyone to keep track of,
this is why game depts have officers, to help see you know what the real rules are in YOUR area!