## 3 The Ambiguity of Virtual Reality Terminology in Healthcare and Beyond
### Modern Definitions and Concepts of Virtual Reality and Related Technologies
Some authors state that such environments allow users to interact with it [36], while others do not mention interaction at all, instead defining non-immersive VR as the user observing or viewing computer-generated images of a virtual environment on a screen [4; 70] or as a virtual environment \"_presented on a flat screen_\" [72]. This lack of clarity is problematic, as such definitions could classify activities where the user remains entirely passive (e.g., watching television) as non-immersive VR. Furthermore, the concept of a 2D screen requires more precise definition. Some virtual environments projected onto 2D screens that entirely surround the user and block their view of the real world--commonly referred to as VR caves--are classified as immersive VR by certain authors [40]. However, according to other definitions, VR caves could be classified as semi-immersive VR environments, which are described as environments that \"_integrate a large display screen for projecting the virtual environment_\" [36]. Based on the definition proposed by [PERSON] et al., (2024) [36], the distinction between non-immersive and semi-immersive environments appears to hinge on the size of the display screen. However, it remains unclear where the threshold for screen size lies. In the field of rehabilitation, non-immersive VR is often referred to as \"exergames\" or \"active video games\" which represents a combination of exercise and gaming [73]. This terminology likely arises because VR is frequently used in rehabilitation for exercise-based interventions. Additionally, exergames often rely on technologies such as _Nintendo Wii, Xbox_, and _PlayStation_, which many authors in healthcare classify as \"non-immersive VR\" [73; 74]. It therefore seems that exergames are a subcategory of less immersive VR experiences that require patients to perform physical exercises. However, since some researchers state that exergames occur within less immersive environments [73; 74], this raises the question of how to classify immersive VR experiences that also require patients to perform exercises. Alternatively, it may be necessary to revise the definition of exergaming to additionally include experiences involving immersive technology. Another term frequently used to describe VR interventions in healthcare is \"serious games\". Serious games are defined as games designed with a purpose beyond entertainment and are utilized to promote users' mental, physical, and social well-being [75]. It can be summarized that serious games represent a subcategory of VR, which can be further divided into exergames--a specific type of serious game focusing on exercise-based activities. In the context of the treatment of musculoskeletal disorders and chronic pain, immersive VR appears to be predominantly limited to the use of HMDs. For example, immersive VR in this field is described as: \"_achieved through HMDs..._\" [36]; \"_involves the use of HMDs..._\" [70]; \"_involves utilizing an HMD_\" [4]; and \"_VR is considered immersive when an HMD is used_\" [76]. It seems that in addressing musculoskeletal issues, researchers primarily classify immersive VR as technology that engages vision, without incorporating other sensory modalities, such as touch, which could be facilitated by additional equipment like haptic technology. This may be due to the limited availability or high cost of such equipment, which makes its inclusion in studies less feasible. Another possible reason is that, particularly for patients with chronic pain who have a reduced capacity to process information, additional haptic technologies may not be used because some authors highlight the risk of information overload caused by excessive multisensory input [77]. Sensory overstimulation could result in negative outcomes such as increased stress, frustration, or even trigger kinesiophobia or catastrophizing in this population group [77].