Nielsen Ratings are a system used to measure the popularity of television programs in the United States. They provide data on how many people are watching a show, which helps networks and advertisers understand audience preferences. This information is crucial for determining advertising rates and scheduling programs. The ratings are collected through a sample of households that have Nielsen boxes installed, which track what shows are being watched. This data is then extrapolated to estimate the viewing habits of the entire population. As a result, Nielsen Ratings play a significant role in the television industry.