What does literacy mean to me?

The dictionary told me that "literacy" means the ability to read and write or the ability to use language proficiently. The first impression this definition gave me was a vague definition. How well a person can use language can be called proficiently? For example, I, I can read most of my textbooks and write some not short articles in English, can I say I have literacy? I cannot understand some awkward biological nouns in English and I cannot always express my feeling exactly, so I do not have literacy? It seems that there is not a gap between literacy and illiteracy. What is more confusing, I will confidently say that I have literacy, if I am asked in China; but I will ask for the clear standards before I can tell whether I am literacy or illiteracy, if I am asked in the US. I think, literacy also depends on which language you are talking about. Anyway, in my opinion, literacy is the ability to pass on your ideas to the others and to understand the others’ ideas.