Electrolytic capacitors use a conducting surface inside a liquid electrolyte. They do not charge and discharge as rapidly as film capacitors do. They have polarity and so they have to be attached correctly. There are two leads; one will have a + and the other a -. This means one lead is "positive" and one is "negative". There are two different styles: axial, where the leads are connected to each end, and radial, where the leads are connected to one end. Electrolytic capacitors are printed with capacitance and voltage rating.