Electro-hydrostatic Actuation Systems (EAS) successfully combine the advantages of electro-mechanical actuation - such as high-energy efficiency and low noise emission - with the benefits of electro-hydraulic technology –which include robustness and the precise handling of large forces. This paper defines keywords like EAS and Electro-hydraulic pump unit (EPU), and provides a comparison of the two technologies. Given the wide range of EAS technology topics, it is only possible to briefly introduce and discuss these in this paper. This technology has reached a level that renders it a strong mechanism for machine manufacturers to support existing and future motion control requirements.