Same thing as affiliate tracking. A unique ID attached to the links you use to send traffic to the merchant that is specifically for you to track your sales for or referrals to the merchant. Example of a tracking code in a link: merchant.com/?ID=YOURUNIQUEID – You'll find an in-depth article on what affiliate tracking codes are and how to use them here.
The General Data Protection Regulation (GDPR), which took effect on May 25, 2018, is a set of regulations governing the use of personal data across the EU. This is forcing some affiliates to obtain user data through opt-in consent (updated privacy policies and cookie notices), even if they are not located in the European Union. This new regulation should also remind you to follow FTC guidelines and clearly disclose that you receive affiliate commissions from your recommendations.
Well duh! If you don’t add affiliate links and banners into your content then how do you expect to make sales? When people fail to make money when affiliate marketing, it is usually because they are not discretely monetizing all opportunities. People DO NOT care if you have a few links and banners on a website, in fact they expect it. Especially when they get interested in a product and want to see more. If they have to go and search for the product themselves, they hate that.
And what about joining another company's affiliate program? It's all about extra revenue. Think about your customers' needs: What other products or services would interest your site visitors? Join those affiliate programs. Affiliate programs can increase your sales with no upfront cost to you. It just takes a little time to plan your strategy and select the partners that will have the greatest impact on your business.