In the context of EDI, a Repository is a location or multiple locations where data is stored and can be retrieved by using a directory to locate the exact location of a particular document.

Merriam-Webster Online Dictionary
repository (noun)
a place, room, or container where something is deposited or stored - depository
a side altar in a Roman Catholic church where the consecrated Host is reserved from Maundy Thursday until Good Friday
one that contains or stores something nonmaterial - considered the book a repository of knowledge
a place or region richly supplied with a natural resource
a person to whom something is confided or entrusted
repository (adjective)
of a drug designed to act over a prolonged period - repository penicillin