CMDG 12: Repeater fields reference
A repeater field is a field that can be duplicated multiple times, reordered and deleted. For a live example of this, check out the Items tab of the Accordion module. There you will see that when you click the Add Item button, another item field is added. This works for any field type, including form fields (as in the Accordion module). The only field types it currently doesn't work with is Editor Fields, Loop Settings Fields, Photo Fields, and Service Fields.
An array of values for each of the repeated fields.
Creating a repeater field is simple. Just set the
multiple value in the field config array to true and your field will automatically become a repeater.
11. Responsive fields reference
13. Sanitize field values