This is used when partner opens a major in 3rd or 4th seat.
Some pairs play these bids inverted but it does not matter which so long as both partners play the same one.
What do you do if you have a real minor suit?
You have to bid 1NT or 2NT if enough points.
We tend to open very light in 3rd seat so responder must keep this in mind with a hand not suited for Drury but with an 11 count. Do not jump to 2NT but bid only 1NT. Partner with a real hand will bid again and then you can show your full hand.