I think what that means is the advertisers don't know your identity as a target. Facebook shows them filters for whom the advertisers want to serve their ads.

I think what that means is the advertisers don't know your identity as a target. Facebook shows them filters for whom the advertisers want to serve their ads. If you click on an ad, then probably your identity is shared, not otherwise. This is based on my limited knowledge of display advertising, so please correct me.