the word may be interpreted into various meanings in different context. Yet generally speaking, you may deem it as "sth of extra/great value", or"things in excess", say,a bonus.
Premium stations here, for example, can be considered railway stations offering a wide range of extra/superb customer services in Melbourn.
yes. And it's your decision to fit the right meaning in.
When encountered with a polysemous situation, it is ALWAYS the most crucial to refer The Word to The Particular Context. U'll get a slim chance of misunderstanding it then.