One of the most commonly misunderstood concepts about Internet performance is speed and bandwidth. Most people believe that bandwidth and speed are the same thing. For example, it's common to hear "How fast is your connection?" Invariably, the answer will be "3 Mpbs", "8 Mbps" or something similar. These answers are actually referring to the bandwidth or capacity of the service, not speed.
Speed and bandwidth are interdependent. The combination of speed and bandwidth gives users the perception of how quickly a large file loads or gets sent. It doesn't help that broadband providers keep saying "get high speed" when they probably should be saying "get high capacity". Notice the term "Broadband" - it refers to how wide the pipe is, not how fast.
Let's understand what each means.
Speed (a.k.a. Latency):
Latency is delay. It is the amount of time it takes a packet of data to travel from source to destination. Together, latency and bandwidth define the speed and capacity of a network.
Latency is normally expressed in milliseconds. One of the most common methods to measure latency is the utility ping. A small packet of data is sent to a host, and the round-trip time (to travel to the destination host and return back) is measured.
A typical speed (latency) for an average home broadband connection in Australia is between 20 and 80 milliseconds (the first hop to it's ISP). For a cable Internet it drops to about 15-30ms. On Spirit Fibre it is on average below 5ms.
Bandwidth is normally expressed in Megabits per second. It's the amount of data that can be transferred during a second.
Bandwidth and latency are connected. If the bandwidth is saturated then congestion occurs and latency is increased. However, if the bandwidth of a circuit is not at peak, the latency will not decrease. Bandwidth can always be increased but latency cannot be decreased. Latency is the function of the electrical characteristics of the circuit.