Punitive damages are, in general, increases to the base damage award, usually by 2x's or 3x's, etc., (I haven't looked up FL's statute yet so...) Example: damages w/o punitives tacked on is $100,000, but with a statute allowing 2x's, it jumps to $200,000, 3x's to $300,000...you get the point.
Since a negligent action is generally one where there was no malicious intent on the part of the wrongdoer/tortfeasor, most states do not alloow punitive damage awards, as the wrongdoer didn't mean to harm the plaintiff.
However, most states do have statutes in place awarding punitive damages in certain, limited instances, including intentional torts, since the wrongdoer/tortfeasor intended to hurt the victim/plaintiff, and also in the areas of toxic waste (think Clean Air/Water Acts), other inherently dangerous things, etc.
In summation, it's a statutory difference that governs the level/degree of damages that are possible, and in FL, pursuant to FL Section 768.72, which I pulled from ZG's recently filed proffer, p. 4 of 8, here:
http://www.forthepeople.com/Zenaida_Proffer_in_Support_of_Punitive_Damages.pdf, punitives are allowable for the intentional tort of libel/slander. The basic idea is to met out more severe punishment to those who intentionally cause harm to others than those who unintentionally cause harm to others.