Support: Percentage of orders that contain the item set. It is a measure of how frequently the collection of items occur together as a percentage of all transactions. For instance, there are 11 orders in total(by different customers) and {bread, butter} occurs together in 3 of them. So, Support(Bread, Butter)=3/11.

Confidence: Given two items, X and Y, confidence measures the percentage of times that item Y is purchased, given that item X was purchased. This is expressed as: Confidence(Y|X) = Freq(X, Y)/Freq(X) This does not tell there is a relationship between two items. The next matric is the one that can tell about it.

Lift: Lift(X, Y) = Support(X,Y)/[Support(X) * Support (Y)] . Lift is the ratio of confidence to the expected confidence. It tells how much our confidence has increased that B will be purchased given that A was purchased.

Lift=1 implies that there is no relationship between X and Y. Lift > 1 implies that there is a positive relationship between X and Y. Lift < 1 implies that there is a negative relationship between X and Y.