If there is very low resistance between two points, which is less than a few ohms, the two points are electrically connected and you’ll hear a continuous sound. This mode is also called as “diode mode”, “buzzer mode”
If the sound isn’t continuous or if you don’t hear any sound at all, it means that what you’re testing has a faulty connection or isn’t connected at all.
Note : if you are testing continuity you must should turn off the system. Turn off the power supply.
Touch the two probes together and, as they are connected, you’ll hear a continuous sound.