It depends on the laptop and if it is a monitor or a television. For most cases an HDMI cable will work. But without know the make and model of the devices you are referring to we can only guess.
In genera most newer laptops may also have a DisplayPort. This can be used to connect external display devices that utilize a DisplayPort cable
. If your external display uses VGA, DVI or HDMI instead, you can also get a DisplayPort adapter cable, allowing you to connect your VGA, DVI or HDMI display to the laptop’s DisplayPort.