Copy Paper
Usually a lightweight paper that is used in copy machines also known as reprographic paper, copier paper, dual-purpose, or xerographic paper. It's generally thin with a small amount of transparency. The grade of the paper is determined by brightness levels which is how light is reflected from the paper. It is the largest category in the uncoated commodity printing paper grade and many governments use it for all of their laser printing, fax, and copier needs.
Printer Paper
Can be any kind of paper that is used in computer printers. Some common examples include laser paper, inkjet paper, and photo paper. Printer paper is available in matte and glossy finishes.
Matte paper has a bright white coating that dries quickly and is recommended for everyday printing.
Glossy paper has a shiny coating that absorbs ink for spontaneous drying. Glossy paper is commonly used for printing photographs, posters, and other images.
Inkjet Paper
Inkjet printers can print on a variety of paper types. It is best to choose a paper based on what you are printing. For example, plain copier paper is usually best for printing emails or other common documents. It provides good results and is relatively inexpensive. If you will be printing in color, a coater paper is usually recommended because it allows for sharper colors and a higher resolution image.
Specialty inkjet papers are available. Common examples include photo paper, glossy paper, business cards, and greeting cards.
Brightness
Contrast is a key element between the toner or ink and the paper. The whiter the paper the better your copies will look. Most paper will have a brightness rating between 80 and 100. Higher numbers represent brighter paper.
Opacity
Opacity is a measure of how well a material prevents light from passing through it. Standard 20# copier paper is somewhat translucent, while heavier papers are more opaque.