We know... choosing a paper weight can be confusing.  Generally speaking, the higher the weight number, the thicker the paper.  But not always...

To help clarify, here is a list of paper styles, weights, and common usages - ranging from thinnest to thickest:

Copy Paper:

20# (thinnest) - basic copies, most economical

Text:

24# - letterhead

60# - (Astrobright) - brightly colored brochures, flyers, and pads

70# - booklets, brochures, flyers, letterhead, and newsletters

Coated Text:

80# - booklets, brochures, and flyers

100# - booklets and flyers

Cardstock and Coated Cardstock:

Index - covers for coil bound books and booklets, certificates, etc. (most economical cardstock)

67# - booklet covers

65# - (Astrobright) - brightly colored coil bound book and booklet covers

            (Astroparche) - certificates

80# - business cards, certificates, rack cards, covers for coil bound books and booklets

100# - postcards, invitations, rack cards, and posters

12pt (thickest) - postcards (coated on one side, uncoated on the other)