Do entries have categories? Searching for e.g. "calculus" only brings up one result. I think the home page needs to say what the site is for and what kinds of

Do entries have categories? Searching for e.g. "calculus" only brings up one result. I think the home page needs to say what the site is for and what kinds of things are on it, otherwise we have no idea what to search for. Maybe start with something in the search box and the results already below?