What are some examples of capacitators?
The simplest kind of capacitor consists of two parallel conducting sheets not touching each other. These are sometimes encased in ceramic. They can have either terminal as their positive or negative.
A slightly more complex kind is a 'dielectric' capacitor, which has a sheet of dielectric material between the two conducting sheets. A dielectric capacitor has a positive and a negative terminal, and can explode if it is wired in backward.
Often the conducting sheets are made of thin metal foil and the dielectric material is a plastic sheet, so the whole capacitor is rolled up into a cylindrical shape and placed inside a case.