A monolight is a self-contained studio flash, that can be powered by an AC or DC battery power and allows fitting of light modification devices, such as reflectors, lightbanks or umbrellas. The light includes a power source and head, contained within a single, compact housing.
Monolights typically have variable output settings allowing to you change their output from full, half, quarter and sometimes down to 1/32’nd power. One of the monolight’s most valuable features is a modeling light that allows you to preview what the flash looks like on your subject and whose output can sometimes be varied to match the output power setting.
In the box, monolights typically always include a synch cord for connecting to your camera using a PC (Prontor-Computer, in case you wondered) cable where it will be directly triggered when you trip your camera’s shutter. Not all digital SLR and mirrorless cameras have a PC connection and so you may have to use a hot shoe to PC adapter to connect the synch cord from camera to main light. Tip: Because of the high voltages across the tip of a synch cord, avoid using a cheapo adapter can fry the electronics inside your digicam. Don’t do it!
If you want to eliminate the synch cord entirely, here’s another suggestion. I’m a bit of a klutz when working in the studio and have, more than once, stumbled over a power cord and more times than I can count, over a synch cord. For me, and others like me, a wireless trigger, like the inexpensive ($99) Pocket Wizard PlusX is the best and safest solution for tripping the light fantastic. It has a range of (up to) 1600-feet and offers 10 channels that are backward-compatible with all other PocketWizard radios and PocketWizard-enabled devices.