Asynchronous versus synchronous
The Indexed Database API specification defines two APIs: a synchronous API and an asynchronous one. Internet Explorer 10 supports the asynchronous API. As a result, database operations do not execute immediately; instead operations return request objects that are executed in the background. Consequently, IndexedDB is an event-driven API. You create requests and then define event handlers to respond to the success or failure of those requests.
The following linked topics show you how to use IndexedDB to open a database, create transactions, and accomplish common database tasks: