The Power Platform ecosystem keeps getting bigger and more capable. Microsoft continues to add functionality to existing components of the platform while simultaneously releasing new ones. One of the newest components (still in preview as of the writing of this blog) to Power Platform is “Cards.”
What are Cards?
Power Apps Cards are small, lightweight applications that can be built without any code and then bolted on to other, larger Microsoft Applications. Cards can be used to add small portions of new business logic that handle very specific functions to your overall business flow without needing to modify your larger applications. Cards appear to be the smallest and lightest Power Platform component to date!
Card Designer
The Card Designer offers a simple UI where a user can drag and drop buttons, table data, images, text boxes, etc. to your card’s form. 
The Card designer appears to follow the modern app designers for other components such as Canvas Apps, with much less overhead or configuration settings.
Connect your Card to a data source
Like many other Power Platform Applications, you’ll want to connect your Card to some data. Typically, you would connect a Card to the Dataverse… (c)
