Electronic payment system that enables customers of a financial institution to conduct financial transactions through that institution's website
From Wikipedia:
Online banking also known as internet banking, e-banking, or virtual banking, is an electronic payment system that enables customers of a bank or other financial institution to conduct a range of financial transactions through the financial institution's website. The online banking system will typically connect to or be part of the core banking system operated by a bank and is in contrast to branch banking that was the traditional way customers access banking services.