You fix the budget, unlike say a magazine where they have a fixed charge for the space irrespective of who saw the advert.
You can't tell the magazine that your ad must be shown to girls aged 12-16. Everyone will watch it!
You can't tell the television channel to show the ad only to middle aged men who still love Kate Winslet.
With Facebook you overcome these obstacles and have a laser-focused audience. This explains why entrepreneurs worldwide prefer Facebook.
I have purchased all the images and I have the rights to use them commercially.(Photo source: https://getstencil.com/?tap_a=9103-1801f8&tap_s=200974-3b53a9 )