SQL syntax question

This SQL statement returns the same result twice even though there is
only one matching entry in the first table "tbl_Drivers" and none in
the second table. Can anyone explain why? I would appreciate it very
much. I am trying to improve my understanding of SQL.
>
SELECT * FROM tbl_Drivers Drvs, tbl_Del_Drivers DelDrvs where
(Drvs.FName = 'Larry' AND Drvs.LName = 'Smith') OR (DelDrvs.FName =
'Larry' AND DelDrvs.LName = 'Smith');