Infinite Sets. If you continue to study this subject you will find discussions about infinite sets, and the idea of different sizes of infinity. That subject has special names like Aleph-null (how many Natural Numbers), Aleph-one and so on, which are used to measure the sizes of sets.
For decades, glossy paper, the type used in magazines, was made using a white clay called kaolin (named after the Chinese region Kao-Ling where it was mined to produce porcelain).
Ruled paper (or lined paper) is writing paper that typically consists of horizontal lines meant to separate lines of hand-written text, and vertical lines meant to provide margins or to act as tab stops. A popular alternative to lined paper is graph paper (square paper or grid paper).