Hi @roro_coeur,
Statistics simply are a form of dynamic metadata that assists the query optimizer in making better decisions. For example, if there are only a dozen rows in a table, then there's no point going to an index to do a lookup; you will always be better off doing a full table scan. But if that same table grows to a million rows, then you will probably be better off using the index.
It is important to remember that statistics are only helpful if they are kept up to date. This can be done with automatic updating statistics or a regularly scheduled (nightly/weekly) update statistics command. Also, index rebuilds will automatically perform a statistics update.
Regards,
Milan
