#Tool

This Combindations calculator / tool gives you a way to generate all the possible combination of a string or group of strings. If only 1 input is provided it gives the combinations of characters in that string and if multiple inputs are provided then it gives combinations of the inputs. Basically, it shows you all the different possible subsets that can be made from the larger set. For this calculator, the order of the items chosen in the subset does not matter.

#Knowledge

In mathematics, a combination is a selection of items from a set that has distinct members, such that the order of selection does not matter (unlike permutations). For example, given three fruits, say an apple, an orange and a pear, there are three combinations of two that can be drawn from this set: an apple and a pear; an apple and an orange; or a pear and an orange.More formally, a k-combination of a set S is a subset of k distinct elements of S. So, two combinations are identical if and only if each combination has the same members. (The arrangement of the members in each set does not matter.) If the set has n elements, the number of k-combinations, denoted by C(n,k) or C_k^n, is equal to the binomial coefficient.

Source: Combination on Wikipedia