What is E-invoicing?
E-invoicing is the exchange of invoices as structured electronic data, not PDFs or paper, so the buyer's system can process them automatically and, in many countries, tax authorities can see them.
In more detail
A PDF emailed to a customer is a digital document, but it is not an e-invoice in this sense. An e-invoice is data in an agreed format, often XML, that follows a national or international standard and travels through an approved channel. Requirements differ by country. Some mandate clearance by the tax authority, some require a network such as Peppol, and others cover only government buyers. Check the rules where you sell and buy, and ask a tax adviser. For finance teams, the benefits are no re-keying, fewer disputes and faster matching. This is general information, not tax advice. Saudi Arabia's ZATCA publishes its own definition, covered in the ZATCA entry.
Example
A supplier's ERP generates each invoice as XML with the required fields and sends it through an approved network. The buyer's system ingests it and matches it to the PO with no reading or typing.