What does this mean? "session opened for user root by (uid=0)"

[barophobia]

Hello,

This seems to be a routine log entry I just don't know what causes it.
On Aug 24th alone I had a total of 479 entries (with corresponding
'closed' entries).

The file line is: Aug 25 14:50:02 servername crond(pam_unix)[9219]:
session closed for user root

I am GUESSING that this is just a message generated everytime some
kind of cron job is run?

Is this kind of output useful for anything or can it be supressed?
(Just seems like kind of a waste of disc space.)


Thanks!
Chris.