This page introduces combinatorics, focusing on counting and key terms like "alphabet," "string," and "permutation." It defines "string" as an ordered set of characters and explains "permutation" as a...This page introduces combinatorics, focusing on counting and key terms like "alphabet," "string," and "permutation." It defines "string" as an ordered set of characters and explains "permutation" as any arrangement of those characters. The text provides examples and includes practice checkpoints for generating strings and permutations of varying lengths and characters.