According to Moses, who is believed to have written the book of Genesis, the seven skinny cows and seven empty ears of corn represent seven bad years where there won't be enough food. It's like a warning to get ready because tough times are coming after seven good years.
Genesis 41:27: And the seven thin and ill favoured kine that came up after them [are] seven years; and the seven empty ears blasted with the east wind shall be seven years of famine.
Genesis 41:27 predicts seven years of famine, while this verse predicts seven years of plenty, providing a contrast in outcomes.
Genesis 41:29: Behold, there come seven years of great plenty throughout all the land of Egypt: