Bandwidth vs throughput; latency, delay and jitter; speed tests vs iperf

Users say 'the network is slow', but slowness can mean several different measurements. Bandwidth is the maximum data rate a link can carry, such as a 1 Gbps Ethernet port or a 500 Mbps internet plan. Throughput is the rate you actually achieve in practice, which is always lower because of protocol overhead, congestion, errors, retransmissions, wireless conditions and the slowest link along the path. A useful picture is a highway: bandwidth is the number of lanes, throughput is how many cars actually get through per minute.