An image tag is a label applied to a container image in a repository that distinguishes a specific image from other images in an imagestream. Typically, the tag represents a version number of some sort. For example, here
v3.11.59-2 is the tag:
You can add additional tags to an image. For example, an image might be assigned the tags
An image ID is a SHA (Secure Hash Algorithm) code that can be used to pull an image. A SHA image ID cannot change. A specific SHA identifier always references the exact same container image content. For example:
OKD provides the oc tag command, which is similar to the docker tag command, but operates on imagestreams instead of directly on images.