This paper provides a systematic literature review and thematic analysis of 92 publications on the Digital Twin from the last ten years. It aims to characterize the Digital Twin, identify gaps in knowledge, and outline future research directions. The Digital Twin is defined as a virtual representation of a physical entity, encompassing a physical twin, a virtual twin, and the data connections between them. Key characteristics identified include the physical and virtual entities, their environments, parameters, fidelity, state, and processes. The paper also highlights seven knowledge gaps: perceived benefits, application across the product life-cycle, use-cases, technical implementations, levels of fidelity, data ownership, and integration between virtual entities. The review emphasizes the need for a consolidated understanding of the Digital Twin to ensure future research efforts are grounded in solid foundations.This paper provides a systematic literature review and thematic analysis of 92 publications on the Digital Twin from the last ten years. It aims to characterize the Digital Twin, identify gaps in knowledge, and outline future research directions. The Digital Twin is defined as a virtual representation of a physical entity, encompassing a physical twin, a virtual twin, and the data connections between them. Key characteristics identified include the physical and virtual entities, their environments, parameters, fidelity, state, and processes. The paper also highlights seven knowledge gaps: perceived benefits, application across the product life-cycle, use-cases, technical implementations, levels of fidelity, data ownership, and integration between virtual entities. The review emphasizes the need for a consolidated understanding of the Digital Twin to ensure future research efforts are grounded in solid foundations.