One thing that needs to be said about vApps is that they actually come in two completely different versions: the vSphere vApp and the vCloud vApp.
The vSphere vApp concept was introduced in vSphere 4.0 as a container for VMs. In vSphere, a vApp is essentially a resource pool with some extras, such as the starting and stopping order and (if you configured it) network IP allocation methods. The idea is for the vApp to be an entity of VMs that build one unit. Such vApps can then be exported or imported using OVF (Open Virtualization Format). A very good example of a vApp is VMware Operations Manager. It comes as a vApp in an OVF and contains not only the VMs but also the startup sequence as well as setup scripts. When the vApp is deployed for the first time, additional information such as network settings are asked and then implemented. A vSphere vApp is a resource pool; it can be configured so that it will only demand resources that it is using; on the other...