Latency is important when someone is directly interacting with another computer, as the amount of lag between the two computers can make some tasks very difficult (such as editing a file). Bandwidth, on the other hand, is not concerned with latency. When downloading a large file, it may be perfectly acceptable to have a 3-4 second wait before the file begins to download. Networking latency is the time it takes for a single packet to go from your computer, to another host and back. Latency is generally measured in milliseconds.