Batiks are a type of fabric often used in quilt making. They are made by a "resist" process where the designer uses wax to prevent dye from penetrating some areas of the cloth, leaving those areas un-dyed. The process can be repeated many times to create complex designs, using many colours.
Compared to other fabrics, batiks have a much tighter weave. This is to help them through the dyeing process, so they can be quite stiff to work with sometimes and don't tend to drape softly like traditional cotton quilting fabric.