If you take a look at the illustration on the right, you will see a diagram outlining the dime defense. The Os in the diagram represent offensive players while the Xs represent the placement of the defensive players.
In this particular dime formation, there are four linemen on the line of scrimmage (imaginary line seperating the offense and defense). You have two defensive ends (DE), one on each end of the line, and two defensive tackles (DT) in between. Behind the defensive line is one linebacker (LB).
Two cornerbacks (CB), one nickel back (NB), and one dime back (DB) combine with two safeties to cover the defensive backfield. The exact position of the defensive backs depends on the type of pass coverage they are in.