Batik is an Indonesian word and refers to a particular method of dying cloth known as 'resist dying', whereby part of the cloth is deliberately prevented from absorbing colour dyes. Instead of a uniformly patterned colour effect, Batik cloth is a vibrant mix of hues, with varying colour intensity on different parts of the cloth.
Wax or paste is commonly used in traditional resist dying - this is applied to various parts of the cloth before the whole is dipped in dye. As the wax is usually applied by hand and the process not exact, a more random colour pattern is achieved, with indistinct, rather than precise borders around the patches of colour. It's a process that has been used in Asia, Egypt and Africa since ancient times.