Items-for-user recommendations use the Recommend Items for User query stage to present items that are similar to ones in which the user has previously shown interest, based on the user’s search history, browsing history, purchase history, and so on. This is one type of collaborative recommendation.
If you have enabled signals and recommendations for a collection, then
<collection>_item_recommendations job is already created and configured to produce items-for-user recommendations (as well as items-for-item recommendations):
This is an ALS Recommender job. See Items-for-User Recommendations Configuration (ALS) for more details.