These measurements describe the paper thickness, which is also known as the paper weight. These numbers help determine how sturdy that paper is. Most of our papers are 12 pt, 14 pt, 80#, or 100#. The thickness of those papers is comparable to higher-quality greeting cards.
To give you an idea of how thick the paper is, our 12 pt and 100# paper measure 0.012 inches. If you need to visualize that, if you place five 12 pt pages in a stack, they'll be as thick as a penny.