https://kubernetes.io/docs/concepts/services-networking/ingress is the resource delegated to configure L7 HTTP access to your cluster services.
An Ingress controller is the actual implementor of the ingress abstraction, here the chef has selected for you one of the finest controllers available: the NGINX Ingress Controller
The certificate manager is an optional component that will cater to all your TLS certificate issuance desires in an automatic and standardized way.
Despite being fit also to in-cluster traffic, this component is mostly useful for securing Ingress resources.
The chef recommends the Jetstack Cert-Manager to accompany the main dish.