A fully qualified collection name (FQCN) is the complete name of an Ansible module, plugin or role, in the form namespace.collection.name. For example, ansible.builtin.copy is the FQCN of the copy module. Using FQCNs tells Ansible exactly which Collection’s code to run.
Short names such as copy still work in many cases, but they can resolve to the wrong module when two Collections define the same name. FQCNs remove that ambiguity, make Playbooks easier to review and are required by many style guides.
Red Hat recommends FQCNs. Steampunk Spotter can enforce FQCN use as a policy and rewrite short names automatically.