There are two basic classifications of fabrics you will come across when laser marking. One type of fabric is known as organic fabric, which is usually plant-based. The most common type of organic fabric you will encounter is cotton. Fabrics made from cotton can include denim and canvas.
The second classification includes synthetic fibers, which can include such products as nylon, spandex, and rayon. Polyester is the most common synthetic fiber you would deal with as it is widely used in consumer products and apparel.
The reason it is important to determine the type of fabric you are about to laser mark is that the laser settings vary depending on the type of fabric you work with. A simple review of the identification tag should give you an idea of the composure and make-up of the material.