ORCID is a standalone open registry, and you'll also find that you're assigned identifiers if your works are indexed in Scopus (Scopus Author ID) and Web of Science (ResearcherID).
The Scopus algorithm uses the article metadata for publications in a journal indexed by Scopus to create Scopus Author Profiles when two or more articles are linked to one author name. Authors with similar names are assigned different Scopus Author Identifiers, but it is the responsibility of the individual author to ensure that citations are accurately assigned to the right identifier.
When you have a publication in a journal indexed by Web of Science, the algorithm assigns you an author record and Web of Science ResearcherID, which you must claim in order to eliminate duplicate records and inaccurate information.