The barebones of an accordion

Highlighting important details of a section and revealing more details upon a tap or click, if necessary.

When and how it should be used?

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What's an accordion?

The accordion is a graphical control element comprising a vertical stacked list of items, such as labels or thumbnails. An accordion is similar in purpose to a tabbed interface, a list of items where exactly one item is expanded into a panel.

What if the user clicks on a collapsed panel while another panel is open?

How to choose an icon to indicate expansion?