if you want to know what a clothing item is go to amazon's (or other retail) Italian site and type the Italian word in. that is how Italians use the word. retailers would not screw that up. some of these words can have multiple meanings. even Italian has synonymous words (sinonimi) in the case of maglia and maglione think of padre and padrone. google 'Italian words suffixed with -one'. in Italian none word for 't-shirt' is 't-shirt'.
I think if for instance camicia means buttoned shirt, we should literally say buttoned shirt as it gets confusing otherwise. Like if you click maglia in this case, it says shirt or sweater is acceptable but really theres a better word for sweater and maglia works only if not buttoned which we dont know.