ESXi is a lightweight, enterprise-class hypervisor developed by VMware that enables the creation and management of multiple virtual machines on a single physical server. It is widely used in data centers to optimize hardware usage, improve scalability, and simplify IT management. ESXi operates independently of traditional operating systems, providing a secure and efficient foundation for virtualization. Its robust features make it a core component of VMware's virtualization solutions, supporting a wide range of applications and workloads.