Ordinary paper is made of wood pulp and other materials like cotton etc. whereas recycled paper contains dispose waste to replace wood pulp.

What are the main types of recycled paper?

Mill broke

Scrap generated in a mill prior to the completion of the papermaking process.

Pre-consumer waste

Material which has been printer, coated or processed but has not been used in its finished form (e.g. envelope clippings and bindery trimmings).

Post-consumer waste

One example is discarded home or office paper that has been printed on and would be buried if not recycled.

Post-industrial waste

Wastes or residues that are produced from manufacturing process. A very good example is bagasse which is residues from sugar cane production process. They will be dumped to the landfill or become another pile of wastes if not used for making paper.

The most common example is cotton paper. Cotton is a natural product which, if not re-used, will become another type of wastes. Using cotton in papermaking fully utilizes our natural resources. Rag from used clothing is another common raw materials used for papermaking.

Lignin is a product found in cellulose plants. This can be washed out when making the pulp. Lignin can make paper weaker and more likely to discolour. For example, newspaper turns yellow in sunlight because of the lignin in the pulp.

For many years virgin fiber was bleached with hypochlorite - a compound that reacts with organic materials and may produce dioxins or its pre-cursors in the reaction. 
Most virgin pulp mills have stopped using this chemistry and are substituting chlorine dioxide in the bleaching stages. This virtually eliminates dioxin and its associated compounds from the waste water. This process is called Elemental Chlorine Free (ECF). Some mills are totally chlorine free meaning they bleach with oxygen, ozone or peroxide. This process is called Totally Chlorine Free (TCF).

Acid-free papers are manufactured in an alkaline environment, which prevents the internal chemical deterioration of the paper over time. The calcium carbonate being added as a buffer also makes the paper resistant to the effects of an external acidic environment.

Wood fibre that are taken from sustainable forest are considered as environmental friendly.
Sustainable forestry is a well - managed planting system which allows enough time for tree growth before they are cut. Under this management every tree is planted and cut with environmental concern.

Materials that, left to itself, will be decomposed by natural process is called biodegradable.