This dissertation investigates the role of Focus-sensitivity for a typology of presupposition triggers. The central hypothesis is that Focus-sensitive triggers require a linguistic antecedent in the discourse model, whereas presuppositions of triggers lacking Focus-sensitivity are satisfied as entailments of the Common Ground. This hypothesis is supported by experimental evidence from two borne out predictions. First, Focus-sensitive triggers are sensitive to the salience of the antecedent satisfying their presupposition, as operationalized via the Question Under Discussion, and lead to interference-type effects, while triggers lacking Focus-sensitivity are indifferent to the QUD-structure. Second, Focus-sensitive triggers are harder to globally accommodate than triggers lacking Focus-sensitivity. The picture that emerges from these results is that the same kind of meaning - presuppositions - is grounded in distinct underlying representations of context in relation to an independent property of the trigger - Focus-sensitivity - which directly affects the way a trigger is processed.