As a headphone enthusiast, here's a reminder/short intro into the common types of headphone drivers, as pretty much all are also used for speakers. I had ChatGPT expand on the paragraphs, so take the audiophile considerations with a grain of salt lol. Nowadays, you can have incredible dynamic driver headphones (e.g. Focal, ZMF), whereas it used to be that the best of the best were planar magnetic or electrostatic.

- Dynamic: Dynamic drivers, also known as moving coil drivers, are the most common type of headphone drivers. They work on the same basic principle as speakers, using a magnetic field to move a coil that is attached to a diaphragm, which then produces sound. The diaphragm's vibrations produce the sound waves that we perceive as audio. Dynamic drivers are used in a wide range of headphones, from budget models to high-end audiophile-grade headphones. Brands such as Sennheiser, Sony, and Audio-Technica use dynamic drivers in many of their models.

- Planar Magnetic: Planar magnetic drivers (also known as orthodynamic drivers) use a thin, flat membrane with a printed voice coil. This is sandwiched between two arrays of powerful magnets that are evenly distributed. When the current passes through the coil, it interacts with the magnetic field and causes the diaphragm to vibrate and produce sound. This driver type is capable of offering excellent resolution and spatial soundstage. Headphones like the Audeze LCD-2 and HIFIMAN Sundara use planar magnetic drivers.

- Electrostatic: Electrostatic drivers consist of a thin, electrically charged diaphragm placed between two stators. The audio signal's changes in electrical charge cause the diaphragm to move, producing sound. Electrostatic headphones are known for their incredibly accurate sound reproduction, including detailed highs and excellent transient response. However, they usually require a specialized amplifier to function. High-end headphones such as the Stax SR-009 and Sennheiser Orpheus HE90 use electrostatic drivers.

- AMT (Air Motion Transformer): AMT drivers utilize a folded diaphragm that moves air significantly faster than the speed at which the diaphragm itself is moving, providing detailed and accurate sound reproduction. The AMT driver's diaphragm consists of a pleated metal sheet, which contracts and expands under the influence of the audio signal in the magnetic field. This type of driver is less common in headphones but can be found in models like the HEDDphone by HEDD Audio.

- Ribbon: Ribbon drivers use a thin metal ribbon suspended in a magnetic field. The audio signal passes directly through this ribbon, causing it to vibrate and create sound. Ribbon drivers are lauded for their transient response and delicate handling of high frequencies. However, they are typically more fragile and less common in headphones. Some high-end models, such as the RAAL-requisite SR1a, employ ribbon driver technology.

edit: forgot to mention, there are also IEM-specific technologies like balanced armatures, but I'm not sure whether those are used for speakers.