User requirements are the business needs of a given software system. In most cases, this is simply the functional requirements of the system.
System requirements refers to the set of behaviors and features of a given software system. This depends on the kind of software application being developed. In most cases, this is simply the non-functional requirements of the system.
Functional and Non-functional requirements have been explained in details here -> https://cpentalk.com/448/requirements-specification-relationships-requirements
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