GSM stands for grams per square meter and is used as a measure of the weight of the wipe material, regardless of the size of the wipe. You may have heard of 80gsm paper, that means 1 square meter of that paper weighs 80grams. Wipes come in many different sizes, so it's important to understand the GSM when comparing different products.
Lighter weight wipes (15-20GSM) are used for economy wipes, and are often 100% polyester. Surface wipes range from 20-30gsm and baby wipes or personal care wipes can be anything from 25-50gsm, with 38-45gsm being common.