Event logs store records of significant events on behalf of the Windows operating system and the applications that run with Windows. Generally, applications should log only information that could be useful in diagnosing a hardware or software problem.
Events are classified as information, warnings, and errors. All event classifications have well-defined common data and can optionally include event-specific data. For example, information can assert that a service has started. Warnings are used for recoverable problems such as low disk-space conditions. Errors are used for nonrecoverable conditions that might cause an application to fail. In addition to logging event classifications, the security service logs successes and failures in audits.