Answer:
Gatsby comes to understand that beauty can be deceptive and can be used to mask darker intentions. He learns this lesson when he discovers the truth behind Daisy's relationship with Tom and the reality of their marriage. He also realizes that money and luxury can be used to create an illusion of beauty and perfection, while at the same time hiding a darker, more sinister truth. Gatsby's realization is ultimately what leads to his death, as he is unable to reconcile the beauty of Daisy with the ugliness of her reality