Knit fabric is fabric that is knitted, rather than woven. Knit fabric typically stretches to some extent.
While the fabric is knitted, it does not look like knitwear, but like fabric.
Knit fabric is used in garments where stretch is required. Sewing them is often done with a serger to maintain the stretch in the seams.
Wikipedia has more to say about knits: Knitted fabric in Wikipedia