Desktop as a service (DaaS), also called virtual desktop or hosted desktop services, is the outsourcing of a virtual desktop infrastructure (VDI) to a third party service provider.
DaaS has a multi-tenancy architecture and the service is purchased on a subscription basis. In the DaaS delivery model, the service provider manages the back-end responsibilities of data storage, backup, security and upgrades. Typically, the customer's personal data is copied to and from the virtual desktop during logon/logoff and access to the desktop is device, location and network independent.
Desktop as a service is a good alternative for a small or mid-size businesses (SMBs) that want to provide their end users with the advantages a virtual desktop infrastructure offers, but find that deploying a VDI in-house to be cost-prohibitive in terms of budget and staffing.
Example from Microsoft:
Source:Internet