Idea that colonists did not have to have direct representation in parliament to be taxed, and that they were not being taxed without represtentation.
The term "virtual representation" was used by the British to argue that colonists did not have to have representatives from the colonies to be represented in parliament. Instead, as British citizens, they were already represented by parliament's current members.
There was massive backlash to "virtual representation" in Britian and the colonies. Colonists firmly held that they had to have direct representation to be taxed.
Anything else--supplemental info, memory pegs, etc.