Cards are the basic unit of a Websites for Trello website. You can arrange them in Lists (which then become categories) or set them up as Standalone pages. In the end, each card in your Trello Board will map to a live page in your website. The card's name will map to the title of the page, the card's description will map to the content of the page.
Just like inside the Trello interface, the special formatting language used to mark up card descriptions (it is called Markdown) is rendered to HTML in the same way Trello does. For example, links written as
[click me!](http://websitesfortrello.com/) are turned into real links: click me!. For more information about Markdown, see this easy guide, a quick example at Wikipedia or the original syntax specification.
Every card in Trello can have cover images. In a Websites for Trello board, if some card of yours have a cover image it will be used and shown as the cover image for that page, and also shown in the lists of cards where it appears.
You can add Trello checklists to your cards, and they will be shown just like actual checklists in the rendered page, right after the description. This can be useful, or don't, you decide.
Any attachment present on a card will also be added to their corresponding pages as a list of links to the actual attachments.
Differently from what happens inside categories sections, cards are shown in the home page according to their creation date. You cannot change the publication date of a card, as it is given and fixed by Trello, but, for your website, you can fake it. Just add a Due date to the card with any date you want and it will be sorted according to it.
Cards with names starting with a
_ are hidden, so you if have some card you don't want to publish yet, just name it
_something instead of
something. When you are ready to publish, remove the
_ and it will be published. This also works for lists and all the cards under them.
What about comments?