Your card summary is the information that is represented on each card (which represents a deal) and is visible while in the pipeline view.
There are four slots of information that can be configured. These can be manipulated by entering the pipeline management section.
Click on the gear icon next to the pipeline name at the top blue bar. Click on the card summary tab.
You will now see a model card that you can edit. Click on the pencil icons to edit the fields, as you select your preferences the pipeline is updated in live time, a green popup on the lower right corner will inform you when the pipeline gets updated.
Click here for a video on using the options available in pipeline management.