After an article has been published, even if it has already passed peer-review, it can still be withdrawn from the scholarly conversation. This is called a retraction. This can happen when problems with the article have been identified by the authors or the readers of the article, who alert the journal publisher that the article is problematic.
This may result in corrections (often called errata) being posted to the next issue of that journal. If the problems are serious enough, however, the article may be retracted.
NOTE that this does not mean the article is removed from databases; often its record will still be retrieved in searches, and may or may not be flagged as a retraction.
Common reasons for retraction include: plagiarism; research is not reproducible; image manipulation; fake data; fake peer review; paper mills; author or publisher error; authorship issues; legal issues.