What are suffix trees and their algorithmic applications?

Suffix trees are compressed tries of all suffixes of a string, built in O(n) time with Ukkonen's algorithm. Applications: O(m) pattern matching, O(n) longest repeated substring, longest common substring of multiple strings, finding all occurrences of pattern, text compression (LZ77). Space is O(n) but with large constants (~20 bytes per character). Suffix arrays are more space-efficient alternatives for many applications.