EC2 Instance (Elastic Compute Cloud) is a virtual machine provided by AWS. It provides on-demand computing resources, allowing users to quickly deploy and scale applications in the cloud. EC2 instances can be customized according to needs, with various combinations of CPU, memory, storage and networking capacity. The user has full control over their EC2 instance and can install any software they require. This makes it an ideal platform for hosting web applications or running intensive workloads such as big data processing.