1、Electrolytic capacitor: the metal foil is the positive electrode (aluminum or tantalum), the oxide film (aluminum oxide or tantalum pentoxide) which is close to the positive electrode is the dielectric, the cathode is composed of conductive material, electrolyte (electrolyte can be liquid or solid) and other materials together, the electrolyte is the main part of the cathode.
2、Ordinary capacitor: isolated conductor and infinity constitute capacitance, conductor grounding is equivalent to receiving to infinity and connected to earth as a whole.

Different composition
1、The same in principle. (1) both store charge and release charge; (2) the voltage on the pole plate (here the electric potential of charge accumulation is called voltage) cannot be changed suddenly.
2、The medium is different. Most of the polarized capacitors use electrolyte as dielectric material, and usually the capacitor with the same volume has a large capacity of polarized capacitor. In addition, the capacity of the same volume of polarized capacitors made by different electrolyte materials and processes will be different. Then there is a close relationship between voltage resistance and dielectric material used. There are also many dielectric materials for non-polarized capacitors, mostly using metal oxide film, polyester, etc. Due to the reversible or irreversible performance of the dielectric, it determines the use environment of the polarized and non-polarized capacitors.?
3、The performance is different. The performance is the requirement of use, and the demand maximization is the requirement of use. If metal oxide film capacitors are used for filtering in the power supply part of the TV set, and the capacitor capacity and withstand voltage to meet the filtering requirements. I am afraid that only a power supply can be installed in the housing. So as a filter can only use polarized capacitors, polarized capacitors are irreversible. That is to say, the positive terminal must be connected to the high potential end, and the negative terminal must be connected to the low potential end. Generally electrolytic capacitors are above 1 microfarad, to do coupling, decoupling, power filtering, etc. Most of the non-polarity capacitors are below 1 microfarad, which are involved in resonance, coupling, frequency selection, current limiting, etc. Of course, there are also high-capacity and high-voltage capacitors, which are mostly used in reactive power compensation, phase shifting of motors, frequency shifting of power supplies, etc. There are many kinds of non-polarity capacitors, so I won't repeat them all.?

4、Different capacity. As already mentioned, the capacitors of the same volume have different capacities, so we will not go into the details. 5. Different structures. In principle, without considering the tip discharge, the capacitor can be of any shape required by the environment. Usually electrolytic capacitors (polarized capacitors) are round, square shape is rarely used. There are many different shapes of non-polarized capacitors. There are many different shapes, such as tube, rectangle, chip, square, round, combined square and round, etc., depending on where they are used. Of course, there are invisible ones, and here invisible refers to distribution capacitors. For distributed capacitance in high frequency and medium frequency devices must not be ignored.

Second, different characteristics
1、Electrolytic capacitor: the capacity per unit volume is very large, tens to hundreds of times larger than other kinds of capacitors. The rated capacity can be very large, can easily do tens of thousands of μf or even several f (but it can't be compared with double layer capacitor).
2、Ordinary capacitors: The types of capacitors can be divided into: non-polarity variable capacitors, non-polarity fixed capacitors, polarized capacitors, etc. from the principle, and from the material: CBB capacitors (polyethylene), polyester capacitors, porcelain chip capacitors, mica capacitors, monolithic capacitors, electrolytic capacitors, tantalum capacitors, etc.