Toggle the visibility of a block-level selector from a button located anywhere in the DOM.
The Collapse Relationship
The collapse mechanism establishes a relationship between a button and its target selctor. With each button press, the target's visibility toggles between show and hide.
<button> tag, the
data-toggle="collapse" attribute is required.
data-target-toggle="#target-id" attribute equals the value of its target selector's
.collapse class is required.
It initially hides the target selector.
id attribute equals the value of its associated button's