Kubernetes taints and tolerations are used to control pod scheduling on nodes, allowing administrators to reject certain pods from tainted nodes. Taints are applied to nodes to repel specific pods, while tolerations are applied to pods to allow them to schedule on tainted nodes. This combination provides granular control over pod scheduling and can be used to dedicate nodes for specific workloads or applications. It also helps in cost optimization by ensuring that only necessary resources are allocated to pods. Additionally, taints and tolerations can be used to automate the lifecycle of spot instances, which offer excess capacity at a large discount but come with the risk of interruption. By using Kubernetes taints and tolerations, administrators can improve the efficiency and reliability of their cluster while reducing costs.