What does it mean migration or conversion?
New Implementation and Landscape Transformation are similar in approach, both involves a setup of a new system and a migration of data (initial data load), while a System Conversion is converting the existing SAP instance into SAP S/4HANA.
S/4 HANA: SAP Business Suit / 4 HANA, meaning that it’s a 4th generation of SAP Business Suit designed to run only on HANA data base