Microsoft releases updates for its operating systems at least once per month, and while some are relatively minor, many of those updates are intended to address important issues. The classifications that Microsoft uses to describe its update releases are as follows:
Critical update. A bug fix that addresses a specific problem not related to security.
Definition update. An addition to the definition database that a product uses to detect viruses or other malware.
Driver. An update to a software component that enables the computer to use a specific hardware device.
Feature pack. An update providing ...