This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Isolation means that no operation outwith the scope of the current transaction can see data in an intermediate state. Basically, if a transaction is updating a row, no other transaction can see that update till it has completed.