E-commerce refers to the buying and selling of goods or services using the internet. It allows for global reach and transactions to occur electronically without the need for travel. While it provides advantages like convenience and reduced costs, e-commerce also faces challenges such as security issues, lack of personal touch, need for internet access, and credit card fraud. The main types of e-commerce include B2B (business to business), B2C (business to consumer), C2C (consumer to consumer), and C2B (consumer to business).