Network latency is the time it takes for a data request to get from the computer making the request, to the computer responding. Including the time it takes for a byte of data to make it from the responding computer back to the requesting computer. It is generally measured as a round trip delay.

Disk latency is the time it takes from the moment a computer, usually a server, receives a request, to the time the computer returns the response.

https://developer.mozilla.org/en-US/docs/Web/Performance/Understanding_latency