The apriori algorithm is an iterative and multiphase algorithm used to generate association rules. It is based on a generation-and-test approach. 

Before executing the apriori algorithm, we need to define two variables: support_threshold and Confidence_threshold. 

The algorithm consists of the following two phases:

• Candidate-generation phase: It generates the candidate itemsets, which contain sets of all itemsets above support_threshold.
• Filter phase: It filters out all rules below the expected confidence_threshold.

After filtering, the resulting rules are the answer.