Windows XP - Chkdsk Command

Can Anyone tell me what the chkdsk command does or fixes?

chkdsk c:/r (is run from the windows Run Command box)

The reason Is,I Ran the command chkdsk d:/r on my seconday Drive and on the 1st or 2nd operation it fixed the following:

deleting corupt file record segment 630

so Now I Am curious if it deleted anything important that I Need for any of my saved data

 

This link will explain chkdsk and its parameters.
http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/chkdsk.mspx
Read also this :
http://support.microsoft.com/kb/q169404/
Personally I always run "chkdsk c:/f " or "chkdsk d:/f "

 

Can be accessed simply from a right click on drive and select, properties, tools. It will prompt you to do it on the next reboot.