If you have an infinite budget, I could 'target' you by purchasing every ad on the internet with the copy "hi bawana, click this link!" Nearly every impression

If you have an infinite budget, I could 'target' you by purchasing every ad on the internet with the copy "hi bawana, click this link!" Nearly every impression would be seen by the wrong person, but a few of the impressions would be seen by you. The rest of the exercise is figuring out how to segment the audience based on whether it's likely/unlikely that you're in the segment. If I know you're from the US and live in California, I can geo-target to that region.