What's the major item for specifying a paper?

Question

like weight, thickness

Answer 1

One thing that makes a good paper is that it is acid free. You should keep it in mind if you want to the paper to last more than a few years.

Answer 2

I believe the most common is 20lb. white for copiers, faxes, etc... Card stock is usually much heavier, like 60lb., 80lb.

It has been a while since I worked in the printing industry, but 18-20lb. is most common for office paper.

Hope this helps!