Knit fabrics are made from one continuous thread, much like a knitted sweater. Knits are wonderful for use in clothing, because they are stretchy and comfortable. They're perfect for making tees, tops, loungewear, and dresses.
Studio Fabric Shop carries a few different types of knits, including light-medium weight jerseys made from cotton and bamboo, heavier cotton interlock fabric, and french terry, which has extra loft due to tiny loops on the back. Whatever knit you're using, be sure to prewash before sewing, especially if you're making clothing.