Capacitors are divided into two mechanical groups: Fixed capacitors with fixed capacitance values and variable capacitors with variable (trimmer) or adjustable (tunable) capacitance values.

The most important group is the fixed capacitors. Many got their names from the dielectric. For a systematic classification these characteristics can't be used, because one of the oldest, the electrolytic capacitor, is named instead by its cathode construction. So the most-used names are simply historical.

The most common kinds of capacitors are:

• Ceramic capacitors have a ceramic dielectric.

• Film and paper capacitors are named for their dielectrics.

• Aluminum, tantalum and niobium electrolytic capacitors are named after the material used as the anode and the construction of the cathode (electrolyte)

• Polymer capacitors are aluminum, tantalum or niobium electrolytic capacitors with conductive polymer as electrolyte

• Supercapacitor is the family name for:

  • Double-layer capacitors were named for the physical phenomenon of the Helmholtz double-layer

  • Pseudocapacitors were named for their ability to store electric energy electro-chemically with reversible faradaic charge-transfer

  • Hybrid capacitors combine double-layer and pseudocapacitors to increase power density

• Silver mica, glass, silicon, air-gap and vacuum capacitors are named for their dielectric.

  In addition to the above shown capacitor types, which derived their name from historical development, there are many individual capacitors that have been named based on their application. They include:

  • Power capacitors, motor capacitors, DC-link capacitors, suppression capacitors, audio crossover capacitors, lighting ballast capacitors, snubber capacitors, coupling, decoupling or bypassing capacitors.

  Often, more than one capacitor family is employed for these applications, e.g. interference suppression can use ceramic capacitors or film capacitors.

  Other kinds of capacitors are discussed in the #Special capacitors section.
  Dielectrics

  The most common dielectrics are:

  • Ceramics

  • Plastic films

  • Oxide layer on metal (Aluminum, Tantalum, Niobium)

  • Natural materials like mica, glass, paper, air, SF6, vacuum

  All of them store their electrical charge statically within an electric field between two (parallel) electrodes.

  Beneath this conventional capacitors a family of electrochemical capacitors called Supercapacitors was developed. Supercapacitors don't have a conventional dielectric. They store their electrical charge statically in Helmholtz double-layers and faradaically at the surface of electrodes

  • with static Double-layer capacitance in a double-layer capacitor and

  • with pseudocapacitance (faradaic charge transfer) in a Pseudocapacitor

  • or with both storage principles together in hybrid capacitors.

Source: Wikipedia