Association rules is a method of data mining . The idea is to find a statistical association between some items in a large set of items, e.g. items purchased in a supermarket by a customer in one visit.
In contrast to deterministic (non-statistical) rules, that are formulated as strict "if/then" rules, the association rules are formulated in statistical terms. For example, a statistical rule might be: "if items A and B are purchased by a visitor to a supermarket, then item C is also purchased by him with probability 60%".