Network performance refers to how well a computer network operates, focusing on factors like speed, reliability, and efficiency. It measures how quickly data can be transmitted between devices, often expressed in terms of bandwidth, which indicates the maximum data transfer rate. Key metrics for assessing network performance include latency, the time it takes for data to travel from one point to another, and packet loss, which occurs when data packets fail to reach their destination. High performance is essential for applications like video streaming and online gaming, where delays can significantly impact user experience.