Hi!
It pretty much works like a table. The user defines rows and specifies content for cards. The card format is mostly given by some CSS. Here’s an example of usage:
{{row classes="home-card-row"}}
{{card title="[[XWiki>>Main.WebHome]]" buttons="no" image="xwiki.png" top-bgcolor="" link-bgcolor="" classes="col-lg-4 col-md-4 col-sm-6"}}
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
* [[Link with my own colors>>url:http://www.xwiki.org]]
{{/card}}
{{/row}}
For now, I would split the code into two macros: one that will display any type of content using Bootstrap columns & rows (to create a table aspect) and one that will apply CSS over the content to give the aspect of a card.
For naming, I was thinking of displayer-bootstrap-grid and displayer-cards-format, but I think they’re not so expressive.