The Pledge Manager is a tool Kickstarter project creators use to improve the post-campaign experience for backers. Once the campaign is complete, an online store (the Pledge Manager) will open up and allow you to add stuff to your pledge. It uses funds from your pledge (so any extras for add-ons can be applied to in-store add-ons). But it also allows you to add funds even after the campaign is over.
Pledge Manager helps me collect information like orders and addresses and will be the primary method to collect shipping.