Hefestos wrote:-- 你想学中文还是日文?
Do you want to study Chinese or Japanese?
Do you want to study either Chinese or Japanese?
Yes, that's right.
The first sentence means "which one do you want to study?" and the second sentence means "do you want to study one of these?".
I'll just add that "或者" is the only translation of "or" used in affirmative.
Rather off topic: Well, in a way, "还是" can be used in affirmative sentences, but there it doesn't mean "or". This happens in sentences like:
(A: You're really not going with me?
B: Sorry, I'd rather not go.)
Marcel, I just checked in Wenlin (;)) and it gives the following examples:
还是家好。 Home is best after all. (On n'est jamais mieux que chez soi.
天冷了，你还是多穿点儿吧。It's getting cold. You'd better put on more clothes.
Here you can also say: 天冷了，你还是多穿件衣服。(你还是多穿一件衣服)