It's a technique created by NaturallyCurly members to keep curls on top of your head while you sleep, to prevent them from being flattened. The result resembles a pineapple! There are step-by-step instructions here http://www.naturallycurly.com/curlreading/hairstyles/how-to-pineapple-your-hair
It's where you gather your curls on top of your head and put it in a pony tail, but on the last "loop", only pull it through part way. The result is a protective "bun" style that keeps curls defined and dent free. It's most commonly used for sleeping.