The chapter is about data structures for text indexing. They are used as fundamental tools in a large amount of algorithms, represented by special arrays and trees associated with texts. The main data structures related to text algorithmics are Suffix trees and automata, Suffix arrays as well as dictionaries of basic factors. All represent all factors of a text in a compact way. For special words they are of a very specific form. Many problems in this chapter are related to such structures with emphasis on their applications. Also de Bruijn graphs are shown as tools for creating special non-trivial words: dense and perfect words.

This is a preliminary text introducing the terminology, basic concepts and tools for the next chapters. It reflects six main streams in the area. At the beginning some basic combinatorics related to words is introduced. Then several important classes of words: Fibonacci, Thue-Morse and de Bruijn words. It is followed by a description basic structures for handling texts, like suffix trees, suffix arrays and de Bruijn graphs and by some elements on text compression. The chapter ends with the important issue concerning pseudocodes of algorithms. Their presentation is done in a simple and understandable form since this is a central element of the book.