Most headphones use a dynamic driver set-up, also known as moving coil drivers. These are the staple choice for headphones. Using air compression to rapidly move an ultra-thin coil of wire, sweet sound waves are produced for you to hear. It’s hard to go far wrong with dynamic drivers as they are effective for all budgets and can produce powerful bass, with crisp, quality sound.
Alternatively, you have electrostatic driver headphones, which work by placing a static (non-moving) electric charge on a film that floats between two perforated metal plates. When audio voltages are applied across the plates, static cling and repulsion cause the entire film to move all by itself. This film is so thin that it weighs less than the air around it, and has no resonances or energy storage, which leads to the colouration inherent in moving coil speakers.
So if electrostatics are so superior, why aren't they more popular? Easy: they require a high-voltage power supply, which usually means use at-home use only, with a hi-fi and/or dedicated headphone amplifier. These types of headphones are typically rare and expensive.