Fabrics fall generally in two categories: Knits and Wovens. In a nutshell your t shirts are made from knits and your button up shirts are made from wovens.
Woven fabric is produced through weaving two sets of yarn. Examples include button up shirts, trousers, jeans, denim jackets.
Knit fabric is produced by interloping (or knitting) one set of yarn. Examples include leggings, t shirts, sweaters, underwear.
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