Capacitors may seem simple enough, but specifying them has actually grown more complex in recent years. The reason why comes down to freedom of choice. The universe of capacitors has expanded greatly over the past few years, in large part because of capacitor designs that take advantage of advances in conductive polymers.
These advanced capacitors sometimes use conductive polymers to form the entire electrolyte. Or the conductive polymers can be used in conjunction with a liquid electrolyte in a design known as a hybrid capacitor. Either way, these polymer-based capacitors offer a performance edge over conventional electrolytic and ceramic capacitors
Panasonic have published a hugely useful white paper that explains everything the average engineer will need to know about polymer and hybrid capacitors. You can download this document here, and whilst it might not make you an industry expert, it will take the mystery out of polymers and will let you design with confidence.