Remarketing involves showing ads to people who have previously engaged with a brand by visiting its website or interacting with it in other ways. It allows targeting valuable users like those who abandoned shopping carts or subscribed to email newsletters. There are different types of remarketing campaigns including standard display ads, product-specific ads, and search ads. Remarketing has benefits like reaching potential customers when they are most likely to buy and using tailored lists for people like abandoners. The remarketing process involves tagging websites, creating rule-based audiences, and building remarketing ad campaigns to those audiences while tracking results.