A VMware vApp is a collection of virtual machines (VMs) and sometimes other vApps that host a multi-tier application, its policies and service levels.
VApps allow disparate VMs to work together in a stack as an application, and support cloud computing architectures. Administrators can nest vApps within vApps, set up VMware resource pools and deploy new vApps based on existing ones.
VMware vApps operate on the Open Virtualization Format (OVF) standard and vApps are exported in OVF format. VMware vApp meta data resides in the vCenter Server database.