Shopify permalinks are a handy way to add items to the cart in emails or other offsite links. There are cases when you might don't want to checkout, but rather just fill the cart.
There's really no such thing as a cart permalink but calling it that makes sense in this context. All the url below does is simulate the same action that a <form> would.
The numbers in the url are the variant IDs.
Head to the Shopify help docs if you're interested in real permalinks.