A free radical is defined as an uncharged atomor molecule which as at least one unpaired electron (therefore not the Oxygen anion). In this particular dop point you are asked to compare properties of oxygen free radical (O) with the molecular oxygen (O2). If you are answering this as a HSC questions, you would do the following:
1. draw the lewis structure of both O and O2
2. lable the 2 unpaired electrons on the O molecule (as crosses)
3. explain the difference in reactivity of the two in terms of the unpaired electons of the free radical and other properties if applicable
Next time when you come across something that you don't undrestand, such as "free radical" in this case, finding the definition of the keywords would be very helpful in understand the question and answering it.
-------------------
*sigh* you can "discover" most of not everything "in your book"