SAP HANA can be implemented on two environments: on-premise for maximum control, and cloud based for an unbeatable time-value efficiency.
SAP S/4HANA on-premise is deployed on client´s own servers, which require maintenance. Upgrades are released annually and must be tested and implemented by a team of professionals.
SAP S/4HANA Cloud is a SaaS (Software as a Service) platform that lives in SAP´s servers and is maintained by SAP. Upgrades are released quarterly and do not require any involvement on the client´s part.