Men's casual knit shirts are made from fabrics that are created by interlocking loops of yarn, such as jersey or piqué, which gives them a soft, stretchy, and comfortable feel. Woven shirts, on the other hand, are made by weaving threads over and under each other, resulting in a fabric that is typically more structured and less stretchy. Knit shirts are generally more casual and better suited for relaxed settings, while woven shirts often have a crisper appearance, making them ideal for dressier occasions.