Nice tutorial on using a multimeter and continuity –
You might be asking, “What is continuity?” But don’t worry, it’s quite simple! Continuity means, are two things electrically connected. So if two electronic parts are connected with a wire, they are continuous. If they are connected with cotton string, they are not: while they are connected, the cotton string is not conductive.
For some basic circuits you can just look to see where the wires go to determine continuity but it’s always wise to use a multimeter. Sometimes wires break or you’re tired and can’t easily follow all the PCB traces.
Multimeter Tutorial – Learning about continuity – Link.