EC2 (Elastic Compute Cloud) is a service offered by Amazon Web Services (AWS) that allows users to rent virtual computers, known as instances, over the internet. These virtual machines can be used to run websites, applications, and other workloads without the need to maintain physical servers. EC2 provides flexibility, scalability, and cost-effectiveness, enabling businesses to quickly scale computing resources up or down based on demand. It is widely used for cloud hosting, development, testing, and data processing.