Remember Tennessee Ernie Ford singing about his burdens in that wonderful baritone voice? Well, today, WE are the ones with the burden. Our RHO (right hand opponent) opens the bidding, and we've got a heavy load... hands we would have opened 1NT had we been in opening seat.
SO! What should we do? If we hold 15-17/18 pts., AND have a stopper or two in their suit, bid the No-trump. BTW, most pairs play that the No-trump player's Pard can use Stayman and transfers. This is called "systems on."