We started with the basics about the Nexus in previous posts.
(See http://blogs.vmware.com/vsphere/2009/12/tell-me-more-about-the-cisco-nexus-1000v.html)
Now, let's get into further details.
Cisco Nexus™ 1000V is the result of a Cisco and VMware collaboration building on the VMware vNetwork third-party vSwitch API of VMware vDS and the industry-leading switching technology of the Cisco Nexus Family of switches. Featuring the Cisco® NX-OS Software data center operating system, the Cisco Nexus 1000V Series extends the virtual networking feature set to a level consistent with physical Cisco switches and brings advanced data center networking, security, and operating capabilities to the vSphere environment. It provides end-to-end physical and virtual network provisioning, monitoring, and administration with virtual machine–level granularity using common and existing network tools and interfaces. The Cisco Nexus 1000V Series transparently integrates with VMware vCenter Server to provide a consistent virtual machine provisioning workflow while offering features well suited for data center-class applications, VMware View, and other mission-critical virtual machine deployments.