Originally, "electronic commerce" meant the facilitation of commercial transactions electronically, usually using technology like Electronic Data Interchange (EDI) to send commercial documents like purchase orders or invoices electronically.
Today it includes things that may more correctly be termed "Web commerce" -- the purchase of goods and services over the World Wide Web via secure server (HTTPS, a special server which encrypts confidential ordering data for customer protection) with e-shopping carts and electronic pay services, like credit card pay authorizations.
Electronic commerce may also involve the electronic transfer of information between businesses (EDI).
So, e-commerce is the conduct of business communications and management through electronic methods, such as electronic data interchange and automated data collection systems.