A batter always contains water and flour. The difference between dough and batter is that a batter contains more water than flour, making it fluid or at least squeezable. A batter does not become solid until after baking. Apart from flour and water, a batter can also contain fat, sugar, and eggs.
A batter is used as a basic ingredient not only in all sorts of pancakes but also as a tasty coating for other ingredients. If you plan to deep-fry a battered product, you can dredge it in a dry ingredient first, such as flour or breadcrumbs. For the crispiest result, make your batter just before deep-frying, ensure your liquid is as cold as possible and stir as little as possible to prevent a gluten network from forming. You can also use liquids that evaporate faster (e.g. beer or vodka) or rice flour or corn meal. These flours do not form gluten and absorb less fat and liquid.