What are suffix arrays and how are they used in string processing?

Suffix arrays store lexicographically sorted indices of all suffixes of a string in O(n) space (vs O(n^2) for actual suffixes). Construction can be O(n log n) or O(n) with SA-IS algorithm. Combined with LCP (Longest Common Prefix) array, they enable O(m log n) pattern matching, finding longest repeated substring in O(n), and various string problems. They're a space-efficient alternative to suffix trees, used in bioinformatics and text indexing.