Diatonic
Most used by dance groups or in folk music come diatonic accordions with one, two or three rows of keys. For each key, there are at least two vibrating pieces of sugar cane to produce the sound.
Concertina
Concertinas are some of the most varied types of accordions, as different manufacturers usually use their own stylistic approach to its design. With anywhere from four to twelve pages, concert settings have single buttons instead of the fixed chord buttons that are common on other types of accordions.
Chromatic
Chromatic accordions are most commonly used in Russia. They are characterized by a large number of buttons, including six rows of treble buttons and 180 buttons for single bass tones.
Piano
While most accordions use buttons made directly on the side of the instrument, piano tractions include a piano keyboard on one side of the instrument. This add-on is intended for pianists who want a similar set of keys when they start playing the accordion.
Custom accordions
Although there are four main types of accordions, many musicians have accordions to their own preferences. Customization can include more or less keys, different wrist straps and instrument length or reed quality. Accordions are classified as keyboard instruments that act as aerophones. In other words, the accordion player presses the keys and squeezes the instrument to force the air columns through the reeds. This action then produces tones or sounds. There are four main types of accordions.
Source:danspela.com