Both types of marketing can utilize the same marketing strategies, such as SEO, content marketing, social media & email marketing; however, there is a distinctive difference between the two.
In simplest terms, digital marketing is used by companies to promote their products/services, while affiliate marketing is when an individual promotes those businesses’ products in an effort to gain commission & is more of a performance-based marketing model.
The way that I like to remember it easier is that digital marketing is an asset for businesses to use to promote their established business & affiliate marketing can be seen as being an independent contractor who is a partner to said company & only earns on a commission basis dependant on their own efforts.
For example, I have created this website for the sole purpose of advertising products I have found on Amazon. I have used digital marketing tools in the process of making my own website such as SEO, social media marketing through channels like Instagram, TikTok, and this is an example that both digital and affiliate marketing can be both similar & different, like most things in this world.