A deliverable is a specific, countable output the project must produce — with a defined format, size, language and delivery date.
The difference between "social assets" and "6 static posts (1:1), 3 stories (9:16), DE + FR, delivered 12 March" is roughly the difference between a scoped project and an unscoped one.
Every deliverable should carry a format, a quantity, a language, a channel and a date. Missing any one of the five is where scope creep enters.