What is the difference between free and full versions of veeam backup 6.1

The free version, Veeam Backup™ Free Edition, provides a subset of the functionality in the full (paid) editions of Veeam Backup & Replication.

The free and full editions use the same download and install, with functionality controlled by the presence of absence of a license key.
- The software operates in free mode when no license key is present, or when an expired license key is present. There is no limit on the number of hosts, sockets or virtual machines (VMs).
- The full editions require a valid (unexpired) license key, and are limited to the number of host CPU sockets specified in the license key for each hypervisor (VMware or Hyper-V).

as for features, full version contains:
- backup jobs
- incremental backups
- scheduled backups
- Application-aware processing
- Windows guest file indexing
- Instant VM Recovery
- VM replication
- Distributed architecture
- Support for remote backup repositories
- PowerShell and command-line scripting
- Veeam Enterprise Manager