1. Introduction  
2. Construction of the eRASS1 Galaxy Groups and Clusters Catalog  
3. Samples of Clusters of Galaxies and Galaxy Groups  
4. Comparisons with Overlapping Cluster Surveys  
5. X-ray Properties of the eRASS1 Galaxy Clusters and Groups  
6. Population Properties of the eRASS1 Clusters  
7. Conclusions and Summary