EDIFACT (EDI message standard)
EDIFACT is a UN-backed standard that describes how an EDI message is built: which segments it contains, in what order, and what each field means. In trade the messages used most often are ORDERS (purchase order), DESADV (dispatch advice) and INVOIC (invoice).
Out of the whole message set a distributor normally meets a handful. ORDERS is the buyer's order, ORDRSP the supplier's answer (confirmed, line missing, different date), DESADV the dispatch advice describing what is on the pallets, RECADV the buyer's receipt confirmation, and INVOIC the invoice. Each has its place in the process and its own deadline.
EDIFACT is a framework standard, so every large buyer documents its own subset in an implementation guide: which segments are mandatory, how to number lines, which unit codes to use. Two rollouts to two chains differ in the details even though the message carries the same name.
Alongside EDIFACT you meet XML messages, including GS1 XML and buyers' own layouts. For the supplier the difference is mostly technical, because the effort goes into linking message fields to ERP data, and that is done once per buyer either way.
The classic trap is treating DESADV as paperwork. The advice describes what physically travels: how many pallets, what sits on each and which SSCC is on the label. A gap between the message and the pallet surfaces at the buyer's dock and comes back as a chargeback.