What is bandwidth and latency?

Bandwidth is the maximum amount of data that can be transmitted over a network link per unit of time, measured in bits per second (bps, Mbps, Gbps). It is the "width of the pipe" — a 100 Mbps connection can theoretically transfer 100 megabits every second. Throughput is the actual data transfer rate achieved in practice, always lower than bandwidth due to overhead, congestion, and errors. Latency (also called delay or ping) is the time it takes for a packet to travel from source to destination, measured in milliseconds (ms). Low latency is critical for real-time applications (gaming, VoIP, video calls). High bandwidth but high latency is called a "fat pipe" — great for bulk transfers but poor for interactive applications. Together they define network performance: a fast download requires high bandwidth; a smooth video call requires low latency.