A digital twin is a digital replica of a living or non-living physical entity. Digital twin refers to a digital replica of potential and actual physical assets (physical twin), processes, people, places, systems and devices that can be used for various purposes. The digital representation provides both the elements and the dynamics of how an Internet of things (IoT) device operates and lives throughout its life cycle.Definitions of digital twin technology used in prior research emphasise two important characteristics. Firstly, each definition emphasises the connection between the physical model and the corresponding virtual model or virtual counterpart. Secondly, this connection is established by generating real-time data using sensors. The concept of the digital twin can be compared to other concepts such as cross-reality environments or co-spaces and mirror models, which aim to, by and large, synchronise part of the physical world (e.g., an object or place) with its cyber representation (which can be an abstraction of some aspects of the physical world).

Digital twins integrate IoT, artificial intelligence, machine learning and software analytics with spatial network graphs to create living digital simulation models that update and change as their physical counterparts change. A digital twin continuously learns and updates itself from multiple sources to represent its near real-time status, working condition or position. This learning system learns from itself, using sensor data that conveys various aspects of its operating condition; from human experts, such as engineers with deep and relevant industry domain knowledge; from other similar machines; from other similar fleets of machines; and from the larger systems and environment of which it may be a part. A digital twin also integrates historical data from past machine usage to factor into its digital model.

In various industrial sectors, twins are being used to optimise the operation and maintenance of physical assets, systems and manufacturing processes. They are a formative technology for the Industrial internet of things (IIoT), where physical objects can live and interact with other machines and people virtually. In the context of the IoT, they are also referred to as "cyberobjects", or "digital avatars".

Healthcare is recognised as an industry being disrupted by the digital twin technology. With a digital twin, lives can be improved in terms of medical health, sports and education by taking a more data-driven approach to healthcare.

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