A Drag is, as it's name suggests, 'dragging' the stick across the drum to make 2 'buzzed' grace notes with one hand - this is then followed by an accented single stroke with the other hand.
Once you've got to grips with this, we can now go on to look at the 'Drag Rudiments' know as RATAMAQUES. Over the next few days I'll post up three different types of Ratamaque for you to work on.