While it is not easy to understand all of them, at least for me right now, it is important to have a list that we can access easily, and thanks to CloudNative-PG documentation, we have this list:

Resource Description
Node A node is a worker machine in Kubernetes, either virtual or physical, where
all services necessary to run pods are managed by the control plane node(s).
Pod A pod is the smallest computing unit that can be deployed in a Kubernetes
cluster and is composed of one or more containers that share network and
storage.
Service A service is an abstraction that exposes as a network service an application
that runs on a group of pods and standardizes important features such as
service discovery across applications, load balancing, failover, and so on.
Secret A secret is an object that is designed to store small amounts of sensitive
data such as passwords, access keys, or tokens, and use them in pods.
Storage Class A storage class allows an administrator to define the classes of storage
in a cluster, including provisioner (such as AWS EBS), reclaim policies,
mount options, volume expansion, and so on.
Persistent Volume A persistent volume (PV) is a resource in a Kubernetes cluster that represents
storage that has been either manually provisioned by an administrator or
dynamically provisioned by a storage class controller. A PV is associated with
a pod using a persistent volume claim and its lifecycle is independent of any
pod that uses it. Normally, a PV is a network volume, especially in the public
cloud. A local persistent volume (LPV) is a persistent volume that exists only
on the particular node where the pod that uses it is running.
Persistent Volume Claim A persistent volume claim (PVC) represents a request for storage, which might
include size, access mode, or a particular storage class. Similar to how a pod
consumes node resources, a PVC consumes the resources of a PV.
Namespace A namespace is a logical and isolated subset of a Kubernetes cluster and can
be seen as a virtual cluster within the wider physical cluster. Namespaces allow
administrators to create separated environments based on projects,
departments, teams, and so on.
RBAC Role Based Access Control (RBAC), also known as role-based security, is a
method used in computer systems security to restrict access to the network
and resources of a system to authorized users only. Kubernetes has a native
API to control roles at the namespace and cluster level and associate them
with specific resources and individuals.
CRD A custom resource definition (CRD) is an extension of the Kubernetes API and
allows developers to create new data types and objects, called custom
resources.
Operator An operator is a custom resource that automates those steps that are normally
performed by a human operator when managing one or more applications or
given services. An operator assists Kubernetes in making sure that the
resource's defined state always matches the observed one.
kubectl kubectl is the command-line tool used to manage a Kubernetes cluster.