The document discusses market basket analysis and the Apriori algorithm. Market basket analysis is used to discover frequent item sets purchased together in transaction data. The Apriori algorithm is used to find these frequent item sets by scanning transactions to count item occurrences, filtering out infrequent items, and generating candidate item sets. Frequent item sets can be used for applications like cross-selling items, proper item placement, fraud detection, understanding customer behavior, and affinity promotion.