Trauma can become lodged in subcortical regions of the brain, kind of like "Trauma capsules" buried at a particular point in time when the trauma occurred—that is, it was not fully processed.
Frequently, when patients experience brainspotting, they will often say, 'but this issue doesn't make sense,' or 'there is no logical reason for me to feel this way.' This is because trauma is not best thought of with the rational part of the brain. Because of this, talk therapy may have some limitations when it comes to processing trauma.
This is why the therapist uses a pointer, or a wand in the session. There is nothing particularly special, or magical, about the instrument. But in using it, the eyes of the patient become something like a 'lighthouse for the brain' scanning for these trauma capsules.
This approach taps into the patient's own innate ability to access the trauma, process it, and heal the self.