Exclusivity is the agreement to date only each other and stop seeing or pursuing other people.
Exclusivity is a mutual commitment to focus a romantic and usually sexual relationship on each other alone, ending the practice of dating multiple people.
It typically arrives through a defined conversation, sometimes called the exclusivity talk, where both people confirm they are off the apps and not seeing others.
It is a step that often precedes, but does not always equal, calling each other boyfriend or girlfriend.
Because assumptions cause friction, the practical move is to state it plainly rather than guess. A short, direct conversation about exclusivity removes ambiguity and lets both people know exactly where the relationship stands.