An MSSP works with an organization to assess the existing state of security, identify needs, and come up with a strategy to meet cyber security goals and needs.
An MSSP can take care of many tasks on behalf of an organization, including:
Performing penetration testing
Applying patches to apps and software
Managing compliance audits and reporting
Encrypting data for storage or transmission
Mitigating and responding to threats
Some MSSPs act as plugins that provide assistance with a specific element of a security program, whereas others provide managerial expertise and oversight for the entire system.