Toile fabric is a cheaper fabric that is used to make a test garment for a pattern.
The preferred material to make toiles is calico or muslin. In Australia, calico seems the more commonly used, in America it is muslin.
Calico and muslin are used because they are cheap 100% cotton fabrics with an easy to see the weave. You can tear them along both the straight grain and crossgrain to make sure the grainline is correct.
Calico and muslin come in a variety of different weights. Although it is used a lot for test fabrics (which is what a "toile" means), it can't be used for all garments - the toile should be made up in a similar fabric (in terms of weight and drape) to the final garment. if the final garment is a very soft delicate fabric, making a toile out of calico will not give a good indication of how the final garment will look and drape. In these cases, other fabrics should be used for the toile.
On this website, I give instructions for creating your own blocks and a necessary step in this is to make toiles to fit your blocks. For this purpose, calico and muslin are perfect. As they are plain woven fabrics (no pattern design on it), usually beige in color, and they are good for marking the toile to assist in the creation and fitting.