CPA advertisements are centralized by specialized companies that are the equivalent of online media brokers, known as CPA networks. A company approaches a CPA network and negotiates to have their advertisement placed in the network for publishers to subsequently place on their websites. You are the publisher.
As previously mentioned, the advertiser has one of two goals, to make a sale or to build a list of qualified leads. Many opt for building a list as they know that this is the best approach for a sustainable business model that will generate revenues for many years, versus a one-off sale.
The advertiser will provide all the marketing materials, from graphics to text for emails and more, and the campaign will run until, either a certain number of actions has been completed, ergo 500 people have signed up for their list, or until a certain date of expiry.