The document summarizes the Apriori algorithm, which is used to find frequent itemsets in a dataset. It works by joining potentially frequent itemsets from the previous pass and scanning the database to determine actually frequent itemsets. It uses the Apriori property that all subsets of a frequent itemset must also be frequent. The document provides an example applying the Apriori algorithm to a sample dataset and outlines the steps of joining candidate itemsets, pruning infrequent itemsets, and finding actually frequent itemsets. It also discusses some drawbacks of Apriori like generating a huge number of candidates and repeatedly scanning the database.