An external cloud refers to a cloud solution that exists outside of the physical boundaries of an organization. A cloud can be either public or community based or private and is not located on the property owned or utilized by the organization. Although this kind of cloud solution is quite similar to a public cloud platform the process of implementation differs.
An external cloud would involve the sourcing of any cloud solution that's available and can be used along with an internal cloud infrastructure or an internal cloud solution for any business need. There can be various forms of delivery of an externally located cloud. If it’s proprietary in nature, the organization can host and install physical servers at a co location facility of the physical server. The services delivered through this kind of setup matches the services offered by a private cloud however the primary difference is that all physical resources are essentially external to the organization.
When it comes to a non proprietary model, the cloud vendor is responsible for providing the complete infrastructure as well as resources to the selected companies. Such type of cloud hosting solutions are generally not marketed very extensively.