In scrapbooking, a "mat" refers to a decorative element that is used to enhance and frame a photo or other focal point on a page. It is typically a piece of paper or cardstock cut into a shape slightly larger than the photo or focal point, creating a border or frame around it.
mats
How to use Journaling Cards?
Journaling cards are elements that you will more often find in scrapbook kits. Although they started to appear when pocket scrapbooking became popular, they can also be used for other purposes. You don't need to create pocket scrapbook pages to take advantage of those cards. So, what can you do with them?