According to the article " Think Twice: How the Gut's 'Second Brain' Influences Mood and Well-Being ," the second brain consists of millions of neurons that are embedded along the walls of our gut. Neurons allow humans to "feel" the inner world of our gut. What I find intriguing is how the second brain can control gut behaviors independent of the brain functions. Perhaps our "gut feelings" are more significant than we would have thought.
Here is a visual image of the description behind the second brain located inside the guts.
More research and studies is needed to be determined on the workings of the second brain.