vCenter Orchestrator is included with vCenter Server Standard and allows vCenter Orchestrator allows admins to capture often executed tasks/best practices and turn them into automated workflows (drag and drop) or use out of the box workflows. An increasing number of plug-ins is available to enable automation of tasks related to related products, e.g. vCloud Director, Microsoft Active Directory, vCloud Automation Center etc.

New features on vCenter Orchestrator 5.5:
- More efficient workflow development experience
- Improved Workflow Schema
- Improved Scripting API Explorer
- Improved scalability and high availability (new Orchestrator cluster mode)
- vSAN support in the vCenter Server 5.5 plug-in
- Security Improvements
- Improved integration with the vSphere Web Client
- REST API enhancements

Details here: http://www.vmware.com/support/orchestrator/doc/vcenter-orchestrator-55-release-notes.html#new

vSphere 5 introduced newly designed workflows with enhanced ease of use and the ability to launch vCO directly from the new vSphere Web Client.