In cloud computing, Cost & Usage Data refers to the detailed records of costs incurred and resources used in a cloud environment. This data is crucial for understanding and managing cloud costs. It provides insights into how resources are being used, which services are costing the most, and where potential savings can be made.

Cloud providers typically offer Cost & Usage Reports that provide detailed information about your costs and usage. These reports can be customized to include daily or hourly granularity, and can be broken down by various dimensions such as service, region, account, or tag.

A company uses AWS for its cloud services. By analyzing their Cost & Usage Data, they can identify that a significant portion of their costs is coming from unused EC2 instances. With this insight, they can terminate these instances to save costs.