Async APIs are used to execute certain operations using Batch Apex Jobs internally. These Batch jobs are usually used for carts with a large number of line items. You can use standard Salesforce APIs like Database.executeBatch, to trigger the Apex Jobs. IDs of these apex Jobs can be used to track the status of the job. You are notified through email about the completion of the job, as there is no synchronous response from the API.
The following Batch Apex job is described in this section: