This document provides an overview of sleep disorders and sleep measurement tools. It describes the normal stages of sleep including rapid eye movement (REM) sleep and non-rapid eye movement (NREM) sleep. Common sleep disorders like insomnia, sleep apnea, narcolepsy, and parasomnias are discussed. Tools for measuring sleep such as electroencephalography (EEG), electrooculography (EOG), and electromyography (EMG) are also summarized.