Difference between card and block ?

I am not very clear about the difference with card and block ,  can anyone explain a bit ? Thanks

This is a good question. Cards were added to Backdrop CMS as something that acts a bit like a block in some situations, but which is easier to use and even more flexible. 

These are the three default "cards" in every new default Backdrop site. 

You can find and edit these cards in the content menu:

While you could have placed three blocks on the front page that looked like this, blocks behave differently from nodes (or pieces of content) in many ways. For example,  you can not edit blocks in the "content" menu. To edit blocks, you have to go to the layouts page, which is a much more cumbersome and confusing process for many site editors. 

Also custom content blocks are not easily used in views. 

If I want to create a block with content that can easily be edited by a site owner (other than myself), I am inclined to create a "card" which is easy for them to find and edit, but I can still place it directly in a layout using an "existing content" block.

Cards can also be displayed in views, whereas blocks can not (at least not easily). 

So, I think of cards as "content" that I ONLY intend to display using views or inside of existing content blocks. Site visitors will never visit the path for a specific card. 

If you experiment a bit with cards, I think you will start to see where they are useful instead of blocks and where blocks are just fine on their own. I would say more, but I'm afraid it would just make things more confusing.

Maybe someone else can add some of their own thoughts about Cards.

so what's the difference with card and node ?

Technically, the important difference between a card and a block is that a card is a node and a block is NOT a node.

A card can do all the things that other nodes can do. You can edit them in the content menu, you can include them in a node view, they are fieldable, etc. 

You can't do any of those things with a block. 

If you want to add some content to a specific page, but don't need any of those other things, then a block might be the right solution for you. 

But, if you want to create something like a block, but you want it to act like a node, edit it in the content menu, add custom fields to it, or use it in views - then a card will work better. 

I hope this helps.

In fact, these three cards are a block of Views.
If you need to display on the main page (some page) “Latest News”, “New Blog Posts”, “Popular Articles”, “Popular goods” (use the “Statistics” module to determine popularity), you create a Views block of content based, containing the fields “Path to Content”, “Image”, “Heading”, and basic cards serve as an example.

 You can see on this forum page the “Recent Topics” or “Recent Comments” blocks, which, like cards, are Views blocks, display some information based on some content, but without images.

Card is a type of "node". Just like Page and Post are types of "nodes".

We've mostly been sticking to just calling them Content Types which is easier to understand, but they are sometimes called Node Types.

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The other reason someone might use Card instead of block is that it is structured with fields. (You can even add new fields.) Blocks cannot have fields.

By the way, if it's not important to you, you can just delete the card type and the view. And just use blocks. You can always create it again later if your needs change.

I thought the difference is that a card is a node (content type) without a url so it can only be viewed when shown in a view or embedded like a block.