Adult affiliate programs are companies like CrakRevenue which has many different sites in different niches that you can promote as their affiliate and another affiliate sponsor is Chaturbate or XLoveCash. You sign up for their program and they let you make money with them. You get paid every time you send them a visitor that spends some money on their website.
Ad networks are companies like AdSense for mainstream or JuicyAds for porn. So you place ads on your site but you will be paid every time clicks on the ad, no matter if the person converts into a paying customer or not. They usually will pay you only a few dollars for a one thousand of visitors.
Ad networks offer different kind of ads you can put on your site including:
Pop unders will be shown in the background of the site and they are very much hated by surfers because they block the main content.
Adult Display ads are the most traditional ad banners that will be rotated after you put a code in your sidebar or anywhere on the website.
I have always had more success with affiliate programs and do not work with any ad networks because I make less money with them.