Is eNotes used only for English or are there other topics I can ask about? For example, can I ask about economics, Theory of knowledge, physics, math, etc?
It is definitely possible to ask about subjects other than English on this site. Many people ask questions about economics, math, and physics. If you ask questions about a subject that is more esoteric, like the theory of knowledge, you may be less likely to get answers. However, it is entirely possible that there will be people who can answer your questions. Literature questions do make up the bulk of the questions that are asked on here. However, there are also many questions in areas such as math, business, history, economics, and other social sciences.
So, if you have questions in areas other than English, please do not hesitate to ask. We do have educators who can answer a wide variety of questions.