An electroencephalogram, or EEG, is a test that measures the electrical activity of the brain. It uses small sensors placed on the scalp to detect brain waves, which are the electrical impulses produced when neurons communicate. This test helps doctors understand brain function and diagnose conditions like epilepsy, sleep disorders, and brain injuries. During an EEG test, patients typically relax or sleep while the sensors record their brain activity. The results appear as wavy lines on a computer screen, showing different patterns of brain waves. By analyzing these patterns, healthcare professionals can gain insights into a person's mental state and overall brain health.