Liqueur d’expédition:

a liquid containing of mature wine, distilled wine and sugar that is added to a Classic Method sparkling wine after disgorgement. Its “recipe” varies from winery to winery and its exact composition is usually kept secret

Liqueur de tirage:

this is a liquid made from wine, yeasts and sugar (or must in the case of semi-sparkling wines) which, when added to a still wine, causes the prise de mousse