What are the factors to decide the target audience of your Ad - Advertising?

Well, if it was me I have to get to know the product am advertising it defines how the ad is going to be , and it's target audience

Mostly we need to pay attention for an accurate segmentations of all your platforms, the message that you trying to divulge, who are those audience (age, social, economical, geographical analysis...etc), which are the goals of it, which are the supports that you are considering to use, how you will measure the results and evaluate them.

Market research, competition and competitor breakdown, survey groups and target audience segmentation