For a brief tutorial, browse E-Commerce Definition and Solutions from CIO Magazine.
If you need convincing, here are the classic 20 Reasons to Put Your Business on the Web.
A more thorough starting point is The Ultimate Guide to eCommerce Software from Zapier, which provides a step-by-step guide for doing business on the Internet.
To answer the persistent question: "How do I find customers?" refer to this extensive guide to resources from Help Scout: Customer Acquisition Strategies for Entrepreneurs.
You can register to request a copy of the following guidebooks from HubSpot:
Many other reports are available from Shopify: Ecommerce Guides