Unreliable systems are those that do not consistently perform as expected, leading to failures or errors. These systems can be found in various fields, such as technology, engineering, and even social structures. Factors contributing to their unreliability may include poor design, lack of maintenance, or external disruptions. In technology, for example, an unreliable software application may crash frequently, causing users to lose data. Similarly, an unreliable power grid can result in blackouts, affecting homes and businesses. Understanding the causes of unreliability is crucial for improving system performance and ensuring user trust.