Negative temperature refers to a condition in certain systems where the temperature scale is inverted. In this context, it means that the system has more energy than a system at infinite temperature. This occurs in specific physical systems, such as certain quantum gases or magnetic materials, where the population of higher energy states exceeds that of lower energy states. In practical terms, negative temperature does not mean that the system is colder than absolute zero. Instead, it indicates a unique state of matter where the usual rules of thermodynamics are altered. This phenomenon can lead to interesting behaviors, such as laser cooling and Bose-Einstein condensates.