Tagging allows you to provide or label specific versions of an image. This is especially useful when you deploy a specific version and if something goes wrong, you can easily roll back to previous version.
These are simple aliases which can be given to a docker image before or after building an image. If you don’t provide a tag, docker automatically gives the image a “latest” tag.
It may also include lowercase and uppercase letters, digits, underscores, periods, and dashes. In addition, the tag names must not begin with a period or a dash, and they can only contain 128 characters.
Docker images can have multiple tags assigned to them. It may appear as different images when you run the docker images command but notice that they all point to the same image ID.
It is highly recommended to tag the image first before pushing an image to a Docker registry. Without the tagging, the image would be allocated with a random ID during the build stage.