Bandwidth, throughput, and speed
Don’t use these words interchangeably like the average Joe.
It refers to the maximum amount of data transfer per second. Usage in a sentence: Gigabit Ethernet provides a bandwidth up to 1 Gbps. In this case it means the capability of the connection. But, bandwidth also means a range of frequencies used to transmit signals. In this case measured in Hertz.
You can use the word bandwidth in a single sentence with both the meanings as — The bandwidth (capacity) for a fiber connection can carry up to 10 Gbps with bandwidth (range) of 20 GHz.
It is the actual amount of data passing through a media/connection. To summarize, throughput is an actual measure of how much data is successfully transferred from source to destination, and bandwidth is a theoretical measure of how much data could be transferred from source to destination.
Here’s an analogy:
Suppose, a connection is like a bridge over a lake, and each vehicle is a data packet. If the bridge can handle 1000 vehicles per hour at its full capacity, then we are talking about the bridge’s bandwidth. But, what if every vehicle must stop to pay a toll fee? The actual number of vehicles crossing the bridge decreases to say a 100 vehicles per hour. This measure is the bridge’s throughput.
Speed is more of a general term that is often used to give the idea of both bandwidth and throughput. But in technical terms, speed means how much data can be uploaded/downloaded per second through a connection like a LAN.