Paper can be grouped into two main grades based on weight and thickness: Text and Cover.
"Text" is a generic name for a variety of lighter, thinner paper stocks that includes Book, Bond, Writing, Ledger, Offset paper. Text paper is flexible, can be easily rolled and folded and is used for printing flyers, handouts, letterheads, book pages, etc. The paper used in ink jet printers would be considered Text.
"Cover" is a generic name for a variety of heavier and thicker paper stocks that includes Bristol, Index, Tag, and Card paper. It is more durable than Text paper. Cover paper is more rigid and must be scored (i.e., dented or creased) before it can be folded. This type of paper is usually smooth, but can have a texture. It can have either a matte or glossy appearance. Cover/Card stock is often used for mass mailed postcards, business cards, playing cards, invitations, program covers, greeting cards, door hangers, catalogue covers, presentation covers, scrapbooking, etc. At its heaviest, Card stock would be similar to material used for a cereal box.