Usually attributed to Michael Cappelletti and his longtime partner Edwin Lewis, origin of the concept is also claimed by Fred Hamilton, John Pottage and Gerald Helms.
With a strong hand of his own, (13+ HCP) Advancer may think that the defensive partnership could have the possibility of a game call themselves.
Look at the following scenarios: So if Advancer's holding is 14+ HCP and with stops in the other suits, (bearing in mind that partner might have shortage in at least one of them so those stops need to be dependable), Advancer might extend the bidding to 2NT asking Intervener 'are you top or bottom of your points range partner?'.
But with 11+ HCP, thus promising a partnership holding of at least 25 HCPs, Intervener advances to a game call of 3NT.
With only 9-10 HCP Intervener now assesses his shortage points using, possibly, the method of 'Losing Trick Count' and thus decides whether to pass 3♥ or sign-off with a game call of 4♥.
Provided that Advancer has stopping values in the other three suits in his own holding (bearing in mind that partner may not have stopping values in Diamonds, merely 4-card length), the only question for Advancer is whether or not the HCP holding for the partnership is strong enough for 3NT.