SAP ECC(ERP Central component) is the core of the existing SAP Business Suite. SAP Business suite has SAP ECC+SAP CRM + SAP SRM + SAP SCM + SAP PLM . SAP ECC to not be confused with SAP Business Suite. SAP ECC is part of the SAP Business Suite. SAP business suite will run on any DB ( Oracle, MSSQL, IBM DB2 ) including SAP HANA.
SAP HANA is an RDBMS like Oracle, MSSQL, DB2, etc. Specialty is, it's an in-memory, column-oriented database.
S/4 HANA stands for SAP Business Suite four SAP HANA - The backend application layer runs on solely HANA DB and the front end will be developed with SAPUI5( Fiori). In the 3 Tier architecture of SAP system, HANA is the database layer, S/4 HANA is the application layer, SAP Fiori is the presentation layer.S/4 HANA is called the SAP Next-gen Business Suite.
The concept of SAP ECC isn't here. Instead modules like Simple Finance, simple logistics etc +SAP CRM + SAP SRM + SAP SCM + SAP PLM . It is an ongoing project and different modules will be optimized to run exclusively on HANA.
For further knowledge in SAP HANA go with the SAP HANA certification course.