EDI is the computer-to-computer exchange of business data in standard formats. In EDI, information is organized according to a specified format set by both parties, allowing a “hands off” computer transaction that requires no human intervention or rekeying on either end. The information contained in an EDI transaction set is, for the most part, the same as on a conventionally printed document.

Generally speaking, EDI is considered to be a technical representation of a business conversation between two entities, either internal or external. Note, there is a perception that "EDI" consists of the entire electronic data interchange paradigm, including the transmission, message flow, document format, and software used to interpret the documents. EDI is considered to describe the rigorously standardized format of electronic documents.

The EDI standards were designed to be independent of communication and software technologies. EDI can be transmitted using any methodology agreed to by the sender and recipient. This includes a variety of technologies, including modem (asynchronous, and bisynchronous), FTP, Email, HTTP, AS1, AS2, etc. It is important to differentiate between the EDI documents and the methods for transmitting them. While comparing the bisynchronous protocol 2400 bit/s modems, CLEO devices, and value-added networks used to transmit EDI documents to transmitting via the Internet, some people equated the non-Internet technologies with EDI and predicted erroneously that EDI itself would be replaced along with the non-Internet technologies. These non-internet transmission methods are being replaced by Internet Protocols such as FTP, telnet, and e-mail, but the EDI documents themselves still remain.

As more trading partners use the Internet for transmission, standards have emerged. In 2002, the IETF published RFC 3335, offering a standardized, secure method of transferring EDI data via e-mail. On July 12th, 2005, an IETF working group ratified RFC4130 for MIME-based HTTP EDIINT (aka. AS2) transfers, and is preparing similar documents for FTP transfers (aka. AS3). While some EDI transmission has moved to these newer protocols the providers of the value-added networks remain active.

EDI documents generally contain the same information that would normally be found in a paper document used for the same organizational function. For example an EDI 940 ship-from-warehouse order is used by a manufacturer to tell a warehouse to ship product to a retailer. It typically has a ship to address, bill to address, a list of product numbers (usually a UPC code) and quantities. It may have other information if the parties agree to include it. However, EDI is not confined to just business data related to trade but encompasses all fields such as medicine (e.g., patient records and laboratory results), transport (e.g., container and modal information), engineering and construction, etc. In some cases, EDI will be used to create a new business information flow (that was not a paper flow before). This is the case in the Advanced Shipment Notification (856) which was designed to inform the receiver of a shipment, the goods to be received and how the goods are packaged.

There are four major sets of EDI standards:

The UN-recommended UN/EDIFACT is the only international standard and is predominant outside of North America.
The US standard ANSI ASC X12 (X12) is predominant in North America.
The TRADACOMS standard developed by the ANA (Article Numbering Association) is predominant in the UK retail industry.
The ODETTE standard used within the European automotive industry
All of these standards first appeared in the early to mid 1980s. The standards prescribe the formats, character sets, and data elements used in the exchange of business documents and forms. The complete X12 Document List includes all major business documents, including purchase orders (called "ORDERS" in UN/EDIFACT and an "850" in X12) and invoices (called "INVOIC" in UN/EDIFACT and an "810" in X12).

The EDI standard says which pieces of information are mandatory for a particular document, which pieces are optional and give the rules for the structure of the document. The standards are like building codes. Just as two kitchens can be built "to code" but look completely different, two EDI documents can follow the same standard and contain different sets of information. For example a food company may indicate a product's expiration date while a clothing manufacturer would choose to send color and size information.

Standards are generally updated each year.