A concept that was popularized after the book Building a Second Brain by Tiago Forte.
A second brain is an external storage area for ideas, thoughts, and notes. It can be physical, such as a notebook, or digital, such as a website, app, or cloud storage. It allows you to capture and store information so that you can access and recall it quickly and easily. Having a second brain, enables you to free up your cognitive bandwidth, allowing you to focus on the task at hand and think more clearly.
A second brain is a term used to describe the mental space created for storing information, ideas, and thoughts in an organized and accessible way. This can be accomplished through writing, using a journal or notebook, using an app, or using a combination of all three. This mental space can be used to recall information, store ideas, plan projects, and organize tasks. It can also be used to manage stress and anxiety by providing an outlet for reflection and self-expression. Having a second brain can help to increase focus, productivity, and creativity.