What's the difference between accordion and button?
The most obvious difference between accordions is their right-hand manuals. Piano accordions use a piano-style musical keyboard, while button accordions use a buttonboard. Button accordions are furthermore differentiated by their usage of a chromatic or diatonic buttonboard for the right-hand manual.
What is an accordion menu?
An accordion menu is a vertically stacked list of headers that can be clicked to reveal or hide content associated with them. It is one of many ways you can expose content to users in a progressive manner.