Shared Service is about companies centralizing work in a single location to optimize cost & streamline processes.

Outsourcing is when companies assign third party service provider to perform their non-core work in order for them to concentrate to their revenue driven work.

Shared Service Outsourcing (SSO) Delivery Models:

SSO Delivery Model

Click here for youtube video about SSO

*Content are partially refered to Wikipedia, MSC and SSON.