Elephant Journal has the article Gaslighting: The Mind Game Everyone should Know About.
Overall, the main reason for gaslighting is to create a dynamic where the abuser has complete control over their victim so that they are so weak that they are very easy to manipulate.
I took a quick survey around my home office. I found that half of us did not know what gaslighting was.
After the death of her famous opera-singing aunt, Paula (Ingrid Bergman) is sent to study in Italy to become a great opera singer as well. While there, she falls in love with the charming Gregory Anton (Charles Boyer). The two return to London, and Paula begins to notice strange goings-on: missing pictures, strange footsteps in the night and gaslights that dim without being touched. As she fights to retain her sanity, her new husband’s intentions come into question.