The confusion about how to use these terms pops up so regularly that their definitions are worth repeating. British wine specialist Jancis Robinson said it best in the Oxford Companion to Wine and her words still apply. Varietal is an “adjective and descriptive term for a wine named after the dominant grape variety from which it is made. The word is increasingly misused as a noun in place of vine variety.”
We also regularly talk about grape varieties. Pinot Noir is a grape variety or more accurately a vine variety – it is not, however, a varietal. You can drink a varietal wine made from mainly Pinot Noir grapes.
Some of the confusion comes from the mainly North American tendency to call wines with a dominant grape a varietal, turning the adjective into a noun in a kind of shorthand that confuses people elsewhere. In Europe – and it’s my personal preference, for the sake of clarity – we often talk about single grape wines for these. An American varietal wine, if it has relatively large percentages of other grapes, would be considered a blend in Europe.
All of this is a bit illusory if you start asking what grapes are in a wine because in most countries the law allows a varietal wine to have a certain percentage of other grape varieties that might well not be mentioned on the label.