Transacting or facilitating business on the Internet is called ecommerce. Ecommerce is short for "electronic commerce."
Interestingly, I am credited with teaching ecommerce at the business school at the University of Texas at Austin, far before the term "ecommerce" was invented. So, I have had the opportunity to see the earliest versions of ecommerce in the late 80's and early 90's.
Popular examples of ecommerce revolve around buying and selling online.