api server: all the feature available at api server. , front end to control plane. anything want to master , can send to api server.
it can be using http, it consumes json file. internally it communicates with each other.
cluster store:any req is send is stored here. internal communication(worker to master etc.) also stored here. it uses etcd (open source) to store.it should exist in etcd- source of truth.
controller manager: collection of controller. node controller(all the monitoring activities), endpoints controller. watches for changes. helps to maintain desired state.
kube scheduler: watches api server for new pods. assign work to neodes.(affinity/anti-affinity)