ReplicaSets in Kubernetes allow administrators to create multiple copies of the same Pod, ensuring application availability and stability. By using ReplicaSets, users can distribute load across multiple Pods, increase reliability, and scale their applications efficiently. Unlike ReplicationControllers, which use equality-based selectors, ReplicaSets employ set-based selectors for greater flexibility. Deployments can also be used in conjunction with ReplicaSets to provide additional configuration options. The main benefits of using ReplicaSets include increased availability, load balancing, high availability, reliability, and scaling capabilities. By understanding how to create, manage, and scale ReplicaSets effectively, Kubernetes administrators can optimize their applications' performance and ensure maximum uptime.