Probably the best way to understand the meaning of catharsis is to experience it.
Recently, I attempted to help a middle-aged, Eritrean man who wanted me to edit his autobiography. He had witnessed horrors in his country upon his people in the name of Christianity. He was emotionally hard pressed to finish the work quickly, perhaps due to a deadline on his visa. I realized how important this work was to him. Writing about his experiences were certainly serving as a catharsis.
While living in West Branch, Michigan, I participated in a writer's group. One lady wrote about her errant brother. She titled her piece "A Lost Soul--On Purpose?" The man had no property and gifted people with his pearls of poetry. Upon his death, this woman was surprised to see scores of people at his funeral showing. She learned these were people whose lives had been changed through the friendship of her brother; many of these were former drug addicts. So, here was a soul who had been shunned by his family for his errant ways and who had made a difference in the world. Needless to say, this lady was in tears as she did her best to read what she had written to the group. The presentation, undoubtedly, was a catharsis for her.
Personally, I have few cathartic experiences in my life--oh, yes, there are the health-conscious ones--fasting, hydrotherapy, exercise, Violet Flame--more, I guess than I realized. The confessional served partly as a catharsis in the Catholic Church. The problem I had with that was trying to come up with a sin to confess. The greatest cathartic of all, in my humble opinion, is the Violet Flame. When I make calls to the Holy Spirit with violet in my mind's eye, I literally feel the change of energy around me. The Violet Flame is a precious gift anyone can do daily. I AM a being of violet fire; I AM the purity God desires!
I hoped I have given you the experience of catharsis.