In a Fabric or Cloth description What is t130 t150 t180 mean for?

When terms like - T130, T180, 210T, etc. are used to describe fabric, these numbers refer to the total thread count in the fabric PER SQUARE INCH. This helps determine the denseness of a fabric. For example, if two fabric are comprised of same size yarn, a T180 fabric will be more dense than a T130 fabric.