Fabrics are either 1-ply or 2-ply. Once the cotton has been spun in to yarn, it can be used right away used to weave the fabric. In this case fabric is 1-ply indicating one thread woven. To get the best quality and fineness two yarns are spun in to a single one, so be called a 2-ply. Two ply fabrics are generally superior in their quality. 3-ply fabrics are also used rarely.
Higher the thread count, smoother and silkier the fabric; hence more expensive. Thread count often referred to numbers like 50s, 60s, 80s, 100s, 120s upto 330s. Thread count indicates the size of the thread in the fabric and there fore how many threads pre square inch. Higher number means the threads are finer and gives the luxurious feel and a lighter fabric.
To produce the fabric yarns are woven from two directions, one from top to bottom and one from left to right. This technically called Warp and Weft. If 2-ply yarns are used for both warp and Weft the fabric is 2X2 indicating the construction. If one side is two ply yarn and other side is single ply the fabric is 2x1.