To begin with, “paper” is a general term for materials in the form of a continuous sheet or web obtained by deposition of vegetable, mineral, synthetic fibers or mixtures thereof from liquid suspensions on suitable forming devices with or without the addition of other substances. These materials can be coated, they can be impregnated during the manufacturing process and at the end of it, while the materials do not lose their identity as paper. The classic "wet" papermaking process uses water as the liquid.

There is no clear distinction between the concepts of “paper” and “cardboard”.

Cardboard is a material also consisting mainly of plant fibers, differing from paper in its greater thickness and mass per square meter
Paper and cardboard are classified according to various criteria: intended purpose, main consumer property, special characteristics of the product, the specifics of the technology for its production, consumer demand, etc. But at this time there is no single international system for classifying paper products.

Production of products in pulp and paper industry

The raw materials used in production are pulpwood, commercial chips from sawmill waste, waste paper, as well as non-wood raw materials (straw of cultivated cereals; grass, for example, esparto; cotton, flax, hemp, jute and rags containing them; wild annual plants - reeds , reed, etc.).
Primary fiber semi-finished products are produced from wood and non-wood raw materials, and secondary fibers are produced from waste paper raw materials. Primary fibrous semi-finished products obtained at pulp and paper mills (PPM) are transferred to the company's own production of paper and cardboard (integrated production) or are marketed as commercial semi-finished products. Recycled fibers are primarily used in the in-house production of paper, cardboard, and for the production of molded paper containers (egg packaging, electronics, appliances, etc.).

In the pulp and paper industry, a single cellulose fiber refers to a single cell isolated from wood or non-wood plant material. In plant raw materials, cellulose cells are interconnected into wood tissue by an intercellular substance (lignin), therefore, three main methods are used to separate wood tissue into individual fibers: mechanical, combined chemical-mechanical and chemical.
Note that the high-yield fibrous semi-finished product (90–98%) obtained by mechanical processing of wood raw materials is called mechanical (wood) pulp. The semi-finished product produced by a combination of chemical and mechanical processing is called semi-cellulose, which has an intermediate fiber yield of 55–90%. The fibrous semi-finished product obtained by sulfite or sulfate cooking of plant raw materials is designated by the term “technical cellulose” (to distinguish it from cellulose found in wood), the yield of which is 40–55%.

For the production of paper and cardboard, waste paper (recycled) fiber is widely used, obtained in the process of recycling waste paper.
The insufficient level of consumption and collection of waste paper in our country has focused the preparation of waste paper fibers mainly on simpler technology for the production of sanitary-hygienic and packaging products. Naturally, a smaller share of recycled fiber in the paper and cardboard composition increases production costs.