Thank you Joseph!
Actually, I haven't implemented yet glossaries in my Moodle platform so I was trying to figure out the best approach for my case: your suggestions are really appreciated!
The long version of my need is: in this web site, italian students learn the Japanese language step-by-step, starting from the greetings, then the first words (e.g. about daily life) and so on; each course introduces a set of new words, so I'd like to give an easy entry point for this set to my students (and this implies to create a course glossary, I suppose) and, at the same time, I'd love to give them a comprehensive glossary as a facility if they want to search for a word or if they simply want to use it as a review resource (and this implies that, as long as I write new words in my course glossaries, the same words flow also into the global glossary).
I understood your suggestions but I don't know exactly how to bend the front page-global glossary also to a "local" course usage... If someone clicks on the global glossary in the front page, then he/she should see the comprehensive glossary.
If someone else clicks on the course-version of this global glossary, then the category corresponding to the course should be shown to the user (and it would simulate a course glossary): am I completely wrong?
Now the answers to your questions: (a) is the way I want to use glossaries and I'm using a Moodle 2.1.
Thank you so much for your support, good night!