In brief, we can divide Recommender Systems in the following categories:

Editorial: Suggestions are manually selected and created by the radio or TV channel editor with the expertise of experienced professionals. Linear broadcast media such as traditional TV and radio are based on this type of recommendation.

Collaborative: Tips for a specific user are generated based on judgments or evaluations that other users in the past gave to certain objects at their disposal. After representing such information (users, objects, rankings) through an array, you need to define and quantify a similarity or distance relationship between users or objects that will be recommended. For example, two O and O’ objects are similarly defined if they have been chosen by many users. Then the recommendation might be to suggest O’ to the users who previously chose O. An approach called “item-item”. Or, two U and U’ users are similarly defined if, for example, they have chosen similar categories of objects. In this case, the recommendation might be to suggest to U an object that was previously chosen by U’. An approach called “user-user”.

Content-based: The RS suggests to a specific user a list of objects that are similar to other objects that the same user chose in the past. In this category, the same objects or their descriptions are compared without taking into account the actions and / or ranking that other users might have given. This approach assumes the appropriate definition of similarity or distance between two or more objects.

Demographic: The recommendation of the RS is based on the demographic characterization of the user, taking advantage of information such as age, gender, residence. It is based on the assumption that different demographic segments require different products.

Knowledge-based: Suggestions are based on rules derived from explicit user or object knowledge.

Community-based or Social Recommender Systems: the tips take into account the choices and ratings of our friends on social networks, starting with the evidence that we tend to keep more in mind the recommendations of friends than recommendations anonymous.

Hybrid: The techniques described above are combined to get more precise suggestions, trying to cope with the weaknesses of each method. Many commercial RSs are hybrid.

Context-Aware Recommender Systems: Over the last few years, information about the specific context in which you are located has become increasingly important in creating a hint. The context is defined by a variety of factors such as profile, emotional state, activity, geographic location, atmospheric conditions, and anything else competes in defining the state of the user, object, or interaction between them.