I believe cups (le tazze) and glasses (i bicchieri) cannot be synonymous. Cups come with a handle by the side while glasses don't. (At least in my country they don't.)
How do I know when to use "i", "il", or "gli"?
http://italian.about.com/od/grammar/a/italian-definite-article-forms.htm This should help some.
Shouldn't this be the glasses?
is these glasses (obviously, that sentense was about glasses as a dish) is the same word for glasses people who have problem with eyes wear, or e.g. sunglasses?
in italian language there are 3 different words for the english term "glass"
1) glasses of wine = bicchieri di vino
2) sunglasses = occhiali da sole
3) these bottles are made of glass = queste bottiglie sono fatte di vetro
What is the difference between cup and glass?
For me this answer is wrong. Cup in Italian is tazza. Bicchiere is glass.