A VMware vApp is a resource container for multiple virtual machines that work together as part of a multi-tier application. An example of a multi-tier application is a typical Web-based application where you might have three tiers: Web, application and database; which are often run on three separate servers. For example, you may have Microsoft IIS running on one server (tier 1), IBM WebSphere running on another server (tier 2) and IBM DB2 database running on a third server (tier 3). The three applications on each server all work together and are mostly dependent on each other for the application to function properly. If one part of the tier became unavailable, the application will typically quit working as it relies on all the tiers for the application to work.

vApps provide a method for setting power-on options, IP address allocation and resource allocation, and provide application-level customization for all the virtual machines in the vApp. When you configure a vApp in vSphere you specify properties for it, including CPU and memory resources, IP allocation, application information, and start order.

Because the VMware treats the vApp as a single logical entity comprising one or more virtual machines, Zerto Virtual Replication also enables protecting a vApp as a single entity in a VPG for any vApp defined under an ESXi host.