A Resting State Network (RSN) refers to a group of brain regions that show synchronized activity when a person is not focused on the external environment. This network is typically studied using functional magnetic resonance imaging (fMRI) and is crucial for understanding the brain's intrinsic activity. The most well-known RSN is the default mode network (DMN), which is active during daydreaming, self-referential thought, and memory retrieval. RSNs are important for various cognitive functions and can be affected by different conditions, such as Alzheimer's disease or depression. Researchers study these networks to gain insights into how the brain operates in its resting state and how it may change in response to various stimuli or disorders.