A French cuff is a style of shirt cuff that is closed by a cufflink rather than a button. In addition to requiring cufflinks, a French cuff is approximately twice as long as a traditional cuff. The French cuff does not however extend entire length down the hand, rather it is folded over onto itself to create a double width cuff.
The French cuff is considered to be much more formal than the more modern button clasp cuff, however as formality has waned in modern times it is not as popular of a choice as button cuffs and rarely seen outside of formal events such as weddings, or black or white tie functions. It should be noted however that within the upscale business community there has been a modest resurgence of the French cops in recent times.