Same meaning, simply you can skip "cái" when you speak or write in this case. Some time you must to put "cái" in the sentence, example:
Give me a glove: Đưa cho tôi cái găng tay.
But if you say backward in VNese (same that English sentence): Đưa cái găng tay cho tôi = Đưa găng tay cho tôi.
I'm VNese and I find this hard to explane, even my teacher ; _ ; hope this helpful...
Please take a look at the word 'of' in English http://www.ldoceonline.com/dictionary/of. I'll try to answer your question using the link above.
Most of the time, OF means CỦA (belong to someone/something) [Meaning 1, 2, and 3 in the link]
OF means TRONG, TRONG SỐ (among, between) [Meaning 4]
OF means CHỨA (contain) [Meaning 6] -> CHỨA can be left out
the rest are much more complicated so leave them for later exploration ;)
As you can see: 'a mug of coffee' -> Meaning 6 in the link -> OF means CHỨA -> You can translate the sentence as 'một ca CHỨA cà phê', or simply 'một ca cà phê'. CHỨA can be left out. ;)