Most major software companies will periodically release patches, usually downloadable from the Internet, that correct very specific problems in their software programs.
Microsoft typically releases their security related patches once per month on Patch Tuesday.
Note: The term "hotfix" is often used synonymously with patch and fix but usually only because it gives the impression of something happening quickly or proactively. Originally, the term hotfix was used to describe a kind of fix that could be applied without stopping or restarting a service or system.
Microsoft usually uses the term hotfix to refer to a small update addressing a very specific issue.
In Windows, most patches, fixes, and hotfixes are made available via Windows Update.