Using an image digest can provide stability and ensure that software being deployed is of known versions for auditing purposes. The digest helps specify the version by uniquely identifying a specific set of layers while avoiding the pitfalls associated with image tags. For more information, see the Kubernetes documentation.
References:
https://kubernetes.io/docs/concepts/containers/images/
https://cloud.google.com/architecture/using-container-images
In additional to having a tag assigned (whether it's latest or a specific name or number), images are assigned a hash digest. Specifying that image digest while pulling the image ensures the image being pulled has not been changed. Therefore, it is recommended to edit 'pod:spec:containers:image' field value from : with @.