The default mode network (DMN) is a group of brain regions that are active when a person is not focused on the external environment. It is involved in processes such as daydreaming, recalling memories, and thinking about the future. The DMN helps with self-referential thoughts and social cognition, allowing individuals to reflect on their own experiences and understand others. Research has shown that the DMN is less active during tasks requiring attention and focus. This network includes areas like the medial prefrontal cortex, posterior cingulate cortex, and angular gyrus. Understanding the DMN can provide insights into various mental health conditions and cognitive functions.