An e-invoice is a digital file of a fixed standard that can be "read" by a computer.
EU countries are introducing more and more additional requirements for sending invoices, both to business and to the governament, in order to reduce the share of uncollected VAT.
These changes will not only benefit governments, but also business itself. A common invoice format will reduce costs. This means no more manual input of invoice data and no more documents that appear in automated accounting systems.