IntroductionSleep disorders are known as conditions that have a huge impact on the quantity and quality of sleep. They are common in the general adult population because as the population ages, the prevalence of sleep disorders increases. Sleep disorders are a problem that most people experience as they age. Several decades ago, sleep disorders were known to the population and doctors. Classification of sleep disorders is necessary to distinguish between disorders and to facilitate understanding of symptoms, etiology and pathophysiology allowing appropriate treatment (Michael, 2012). The International Classification of Sleep Disorders (ICSD) is an authoritative clinical text for the diagnosis of sleep disorders. The ICSD book is under review due to many reasons that could have caused the sleep disorder in the patient. The previous version of the book mainly focused on the main symptoms (insomnia, excessive sleepiness and abnormal events that occur during sleep), they were not based much on pathophysiology because most cases of sleep disorders were still unknown . The purpose of this article is to review the differences in symptoms and pathophysiology. As well as critically evaluating the scientific evidence on ICSD that would trigger awareness of the general public's views on the importance of sleep. Literature A search in a PubMed journal was carried out using the “Classification of sleep disorders” section. The resulting articles were filtered in the search for related words. The topics were examined through reading the abstract. Most references cited in these articles have been checked to be in corrected form. Michael J. Thorpy's quote was checked to see if there were any new artics...... middle of article...... the sleep disorder is impressive and it has proven many advantages that would help the doctor to be more accurately determine the information about the patient's sleep disorders.Summary and ConclusionThis literature in this field is very extensive and challenges today's medical technology. Studying and learning new symptoms of sleep disorders is just as difficult as examining the brain where the doctor has to find out how the brain works while we sleep. Various disorders have been classified, but there are many others that still remain unknown to the world. This literature provides knowledge of something we thought was so simple, but very complex in a way that requires more future knowledge. The author has covered most of the important symptoms of the disorders. The ICSD is currently being revised and updated to provide a more accurate diagnosis if a person is suffering from sleep disorders..