Invisible illness refers to medical conditions that are not immediately apparent to others, meaning individuals may look healthy on the outside while experiencing significant health challenges internally. Examples of invisible illnesses include chronic fatigue syndrome, fibromyalgia, and autoimmune disorders. These conditions can affect daily functioning, making it difficult for individuals to engage in regular activities. People with invisible illnesses often face misunderstandings or skepticism from others, as their symptoms may not be visible. This can lead to feelings of isolation and frustration, as they navigate their health challenges without the support or recognition they need from friends, family, or society.