Digital Twins are becoming a key element in the industrial manufacturing sector, offering promising advances in maintenance, particularly in Prognosis and Health Management (PHM) and Life Cycle Management of systems. The evolving development of Digital Twins, alongside their vital role in asset PHM, makes it essential to analyze their current state of the art. This analysis is crucial for guiding the future direction of maintenance practices. Therefore, this study focuses on examining the state of the art of Digital Twins in asset PHM. It involves a systematic bibliographic review that covers the definition of a Digital Twin and extends to its various potential applications in the industry. The findings of this work provide an overview of the current landscape of Digital Twin technology and offer insights into potential future developments. This analysis is key to enhancing the understanding and utilization of Digital Twins, establishing them as a significant tool in modern industrial maintenance and asset management.