I guess the simple answer here is that this is used to timeout any session data, whether it be for the customer or user logins or site accesses.
This is also unimportant information. The fact that the query itself is causing a server timeout (which I assume is what hostgator are telling you) IS important, and in my experience it generally means that the Sessions database table has become corrupted.
You can check/rectify this by running the 'repair database' function provided by phpmyadmin, the 'MySql database' tool found in most cPanels, or almost any other DB administration tool at your disposal.
Cheers
RodG
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