It's just the coloquial term for activation of the Default Mode Network (DMN). And yes, it happens everywhere, all throughout the day and to varying degrees.
Also, it's not necessarily always a desirable thing. For example, the practice of mindfulness is literally cultivating the ability to switch off the DMN. The thing that people don't so often click to is whilst it does sometimes lead to those insightful "shower thoughts", it's also what's behind long night torturing yourself ruminating about an upcoming confrontation you're anticipating having with someone etc.
I spent quite a bit of time reading and understanding about the brain and after understanding that the Central Executive Network and the Default Mode Network operate like a see-saw that's mediated by the Salience Network, a great deal more things made sense to me. It helps to know too that for anyone who has experience trauma where they have an elevated HPA-Axis, that the connections between the Salience Network and the Default Mode Network get stronger and hence slipping into rumination becomes the path of least resistance and thus happens more frequently. Actively practicing mindfulness meditation helps counteract this and instead strengthens the connections between the Salience Network and the Central Executive Network.
After learning about the above I discovered Zen Buddhism and realized they've known this intuitively for thousands of years.
Also, it's not necessarily always a desirable thing. For example, the practice of mindfulness is literally cultivating the ability to switch off the DMN. The thing that people don't so often click to is whilst it does sometimes lead to those insightful "shower thoughts", it's also what's behind long night torturing yourself ruminating about an upcoming confrontation you're anticipating having with someone etc.
I spent quite a bit of time reading and understanding about the brain and after understanding that the Central Executive Network and the Default Mode Network operate like a see-saw that's mediated by the Salience Network, a great deal more things made sense to me. It helps to know too that for anyone who has experience trauma where they have an elevated HPA-Axis, that the connections between the Salience Network and the Default Mode Network get stronger and hence slipping into rumination becomes the path of least resistance and thus happens more frequently. Actively practicing mindfulness meditation helps counteract this and instead strengthens the connections between the Salience Network and the Central Executive Network.
After learning about the above I discovered Zen Buddhism and realized they've known this intuitively for thousands of years.