What is it?  What is so good about it?  How can I use it? 

"Modal is a bio-based fibermade by spinning reconstituted cellulose from beech trees. It is about 50% more hygroscopic, or water-absorbent, per unit volume than cotton is. It is designed to dye just like cotton, and is color-fast when washed in warm water. Modal is essentially a variety of rayon.

Textiles made from Modal are resistant to shrinkage and fading. They are smooth and soft, more so than even mercerized cotton, to the point where mineral deposits from hard water, such as lime, do not stick to the fabric surface. Like pure cotton, modal should ideally be ironed after washing."  Wikipedia