Ideally, in a Sap environment, a three-system landscape exists. A system landscape consists of

Development Server (Dev),

Quality Assurance server (QAS) and

Production Server (PROD)

Development Server (Dev):  In development server you have to make configuration of SAP + Unit testing also the configurations & coding done here.

Quality Server: In Quality server you have to do again some configuration+ Unit / Integration testing moreover

 Production Server: Day to day Transactions posting / SAP End users activities.