Normally, users buy and sell items using the eBay online interface, interacting with eBay directly. But with the eBay API, you communicate directly with the eBay database in XML format. By using the API, your application can provide a custom interface, functionality and specialized operations not otherwise afforded by the eBay interface.
Using the API, you can create programs that:
Submit items for listing on eBay
Get the current list of eBay categories
View information about items listed on eBay
Get high bidder information for items you are selling
Retrieve lists of items a particular user is currently selling through eBay
Retrieve lists of items a particular user has bid on
Display eBay listings on other sites
Leave feedback about other users at the conclusion of a commerce transaction
Because the API is not dependent on the eBay user interface, it allows you to create stable, custom functionality and interfaces that best meet your business needs.
For instance, you can:
Automate the process of listing and monitoring auctions. There is no need to parse eBay pages that change frequently, breaking applications. A seller has access to more tools they can use to sell better and faster.
Extract user information from eBay and automate the end auction management process and delivery to eBay sellers and buyers.
After joining the Developers Program, you will have access to the Developer Zone, a password-protected Web site for members only. The Developer Zone is the primary source