Sharepoint - What is the point of the Error Message Correlation ID in Sharepoint 2010

You can use the ULS logs in the 14-hive/logs, and search for the correlation ID. You will then get all messages related to that correlation ID. You can either look through the text file, or use the ULS Viewer.

Alternatively, you can execute e.g. this Powershell command to get the messages with this correlation id:

Get-SPLogEvent | ?{$_.Correlation -eq "YOUR-CORRELATION-ID-HERE"} |
ft Category, Message -Autosize

The correlation ID is the unique identifier for the request, not for the error itself.

In simple cases, it can be used to quickly search the logs to get a more detailed error message (e.g with a stack trace) than what was shown to the user. You can either search the trace log files or the logging database with that correlation ID and you'll get every log message related to that request. In more complex cases, the error might have been caused by something that happened earlier in the page's life cycle, so being able to narrow your search will get you the information you need faster.

The correlation ID is written to the end of each line in the trace log files, which are by default stored in C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\LOGSlike Tom Halladay said. Alternatively, you can search the WSS_UsageApplication database's ULSTraceLog view, which has a separate field for the correlation ID.