Granny Smith is an elderly Earth pony. She is Applejack, Apple Bloom, and Big McIntosh's paternal grandmother.
History
She and her family were responsible for the founding and growth of Ponyville. During her presentation to the class, Granny Smith explains how she discovered the magical zap apples when she ventured into the Everfree Forest to find food for her family. The jam made from the magical zap apples was so delicious, that ponies gathered from all over Equestria to taste it.
Season 6
While the Gems were working on the farm for the upcoming family reunion, Granny Smith slipped an invitation into Steven Universe's pocket as he was leaving, mainly as a way to get him to come to the reunion.