This will cover the core concepts in kubernetes, mostly for my own use.
Since I know AWS ECS pretty well I will compare som of the concepts with that.
I see that we have two sides:
The ops side and the devs side.

Dev

• a pod is like a task definition, in that it defines one or more containers, a pod can be restricted in its resource use. Pods can communicate with each other like they are on localhost
• a replica set should mostly not be used directly but is used by deployments to scale the number of pods up and down.
• a deployment is a declarative way to tell kubernetes how you want the world to look like, the deployment controller will then make it happen
• a service is a way to expose the pods in a deployment to the world outside kubernetes. you can think of it a bit like a load balancer, that hides the excact location of the downstream websites
• an annotation is used to keep all the different elements organized and when you declare something about a kubernetes element you often select the corresponding element with an annotation
• an ingress is a way to give access to a service to the outside world, by exposing an ip address that is not internal to the cluster
• a job is a one time run of a pod
• a namespace is a way to divide a kubernetes cluster into multiple virtual clusters and hence seperate the services.
• a persistent volume is a way to give a pod access to disk

OPS

• cluster a kubernetes cluster where one can deploy applications, this is basically what kubernetes is .
• node a computer in a kubernetes cluster
• a secret is a way to share for instance a database password
• a cron job is like a line in a crontab
• a network policy is like a firewall that can be used to define how pods are allowed to communicate
• a Pod Security Policy controls the actions a pod can perform