Anything that's not clearly seen or understood is unapparent. The correct solution to a math problem might be completely unapparent to you until your teacher explains each step.
Sometimes, despite your anxiety about speaking in front of a group of people, your nervousness can be completely unapparent to your audience — they don't see or sense it at all. Things that are unapparent are either invisible or not at all obvious. This adjective is formed by adding the prefix un- ("not") to apparent, which shares its Latin root with appear.