I believe you are referring to “interlock fabric.” Interlock is a type of double-knit fabric that is created by interlocking two sets of single-knit fabric together. It is known for its smooth surface, stretchiness, and durability.

Interlock fabric is typically made from a blend of cotton and synthetic fibers, such as polyester or spandex. It is commonly used in clothing, such as t-shirts, polo shirts, dresses, and activewear. It is also used in home decor, such as bedding, blankets, and towels.

Interlock fabric has a smooth surface on both sides, which makes it reversible and versatile. It is also breathable and moisture-wicking, making it ideal for use in activewear and sports clothing.

Interlock fabric can be treated with different finishes, such as dyeing, printing, or embossing, to create different colors and patterns. It is also easy to care for and can be machine-washed and dried.

Overall, interlock fabric is a versatile and durable fabric that is widely used in a variety of applications due to its stretchiness, smooth surface, and breathability.