Outsourcing and offshoring are used interchangeably in public discourse despite important technical differences. Outsourcing involves contracting with a supplier, which may or may not involve some degree of offshoring. Offshoring is the transfer of an organizational function to another country, regardless of whether the work is outsourced or stays within the same corporation/company.
With increasing globalization of outsourcing companies, the distinction between outsourcing and offshoring will become less clear over time. This is evident in the increasing presence of Indian outsourcing companies in the US and UK. The globalization of outsourcing operating models has resulted in new terms such as nearshoring, noshoring, and rightshoring that reflect the changing mix of locations. This is seen in the opening of offices and operations centers by Indian companies in the U.S. and UK.
Multisourcing refers to large (predominantly IT) outsourcing agreements. Multisourcing is a framework to enable different parts of the client business to be sourced from different suppliers. This requires a governance model that communicates strategy, clearly defines responsibility and has end-to-end integration.
source - wikipedia.