The latency time is the period of time that a device (e.g. amplifier) needs to output an input audio signal (e.g. from a CD player) to loudspeakers or to loop through, process and convert a signal.
The latency time is sometimes also called "time to music". This is, for example, the time span from pressing a button on the remote control until the action is carried out (e.g. switching on). The latency time is usually in the millisecond range.
Different latency times when two devices interact (e.g. TV and soundbar) can lead to a time discrepancy (no lip sync between picture and sound). However, this can usually be adjusted in the sound menu.