"The boy loves to learn."
Translation:Drengen elsker at lære.
Well, as far as I know, "at lære" as in "to teach" needs an (in)direct object to work; who is being taught? For example "Jeg lærer dem at læse" - literally "I am teaching them to read", the object "dem" is needed, and if it wasn't there, it would be "Jeg lærer at læse" - I learn/am learning to read". Since the sentence you're asking about does not contain any objects, it can only mean "to learn".
However, teaching is sometimes called "at lære fra sig" lit. "teaching from oneself" and that's the one that would mean "The boy loves to teach" - "Drengen elsker at lære fra sig." You can also use "undervise" as teaching. It is mostly related to educational subjects, but very common. "Drengen elsker at undervise i dansk" - "The boy loves to teach Danish".
It's confusing, I know, and I hope I didn't confuse you any more than you already were! Just ask again if I didn't make any sense