A way to split a big table into smaller tables of hidden patterns.
Imagine a school cafeteria knows your lunch mood. You skip the survey, but it still learns: tacos yes, mystery meat no.
It is used in recommendations and rating guesses. It fills blanks from a few clicks, stars, or buys.
Embedding
Matrix factorization often turns users and items into small vectors.
Unsupervised Learning
It can find hidden structure when clear labels are missing.