The New Bulk API in MongoDB 2.6 introduces a new way of performing bulk write operations, allowing applications to leverage these operations using a fluid style API. The API has two core concepts: ordered and unordered bulk operations, which differ in the order of execution. The ordered operation guarantees the ordering of the operations, while the unordered operation does not guarantee any specific order. The API provides various methods for inserting, updating, removing, and upserting documents, as well as handling write concerns and errors. The results of these operations can return information about individual operation errors in the batch, along with aggregated counts of successful operations. There are implications to the fact that write commands are not mixed operations but either insert/update or removes, which affects the performance of the Bulk API.