In case the system is developed, tested and operated in different hardware environments (i.e. DEV for development, CI for build/integration, TEST for system and manual tests and PROD for production), you should document these environments plus possible differences between them.
The stereotype «executionEnvironment» symbolizes such environments. The little “infinity” symbol in the lower right corner (i.e. in Development) means there is a refined diagram available (that “infinity” symbol is a speciality of Sparx EnterpriseArchitect®).