OVF is a file format that supports exchange of virtual appliances across products and platforms. OVA is a single file distribution of the same file package.
The OVF and OVA formats offer the following advantages:
OVF and OVA files are compressed, allowing for faster downloads.
The vSphere Web Client validates an OVF or OVA file before importing it, and ensures that it is compatible with the intended destination server. If the appliance is incompatible with the selected host, it cannot be imported and an error message appears.
OVF and OVA can encapsulate multi-tiered applications and more than one virtual machine.
Exporting OVF or OVA templates allows you to create virtual appliances that can be imported by other users. You can use the export function to distribute pre-installed software as a virtual appliance, or to distributing template virtual machines to users. You can make the OVF or OVA file available to users who cannot access your vCenter Server inventory.
Deploying an OVF or OVA template allows you to add pre-configured virtual machines or vApps to your vCenter Server or ESXi inventory. Deploying an OVF or OVA template is similar to deploying a virtual machine from a template. However, you can deploy an OVF or OVA template from any local file system accessible from the vSphere Web Client, or from a remote Web server. The local file systems can include local disks (such as C:), removable media (such as CDs or USB keychain drives), and shared network drives.