Bandwidth refers to the maximum amount of data that can be transferred in a unit of time. It is typically expressed in bits per second (or some other similar ways such as gigabytes per second).
Whereas bandwidth is the maximum data can be transferred in a unit of time, throughout is the actual amount of data transferred.
Latency is how long it takes to go from one end to the other. That is, the delay between the sender sending information and the receiver receiving it.
Or more broadly: The delay between a stimulus and the response it triggers in an organism.
For example, search typeahead suggestions are useless if they take more than a second.
The whole point of caching is low latency (amongst other things like reducing DB load, etc.).