What is meant by GSM and Basis Weight?

GSM is grams per square meter and is the weight measure used for designating paper weight in all countries outside of North America.  Basis Weight is the term used for North American paper weights and refers to the weight in pounds of 500 sheets of paper cut to the basic parent size sheet.  Typical paper equivalents between basis weight and gsm for text papers include 50lb/75 gsm, 60lb/90 gsm, 70lb/105 gsm, 80 lb/128 gsm, 100lb/157 gsm. For cover stocks, the equivalents include 10pt/210 gsm, 12pt/ 260 gsm, 15pt/310 gsm.