Platform Ops is the team responsible for curating, maintaining, connecting, and securing the platform that provides Dev, DevOps, SecOps, and (to a lesser degree) NetOps teams with what they need to do their jobs.
A service mesh helps orchestrate containerized environments, routing traffic, defining & enforcing policies, & revealing application availability & security.
A sidecar is a separate container that runs alongside an application container in a Kubernetes pod, acting as a helper application of sorts. Learn more here.
An Ingress controller is a specialized load balancer for Kubernetes environments. It accepts traffic from outside the Kubernetes platform, and load balances it to Kubernetes pods (containers). It monitors pod status and automatically updates load-balancing rules as necessary.
Kubernetes is an open source container orchestration platform. It provides a complete platform for scaling and managing applications that are deployed in containers.