In the US it’s a mainstream eating apple. Which isn’t to say it’s great for eating, considering the ultimate mainstream eating apple is the awful Red Delicious. In for example a gas station, they will stock Red Delicious and Granny Smith so you have your choice of red or green apple. Granny Smith is a better apple than Red Delicious: it’s sweet and pleasantly tart. It’s got a weird texture though. And it’s too hard, as you point out in another comment.

Better second-tier mainstream apples here are Macintosh and Golden Delicious, before you start getting to the premium apples like Gala, Fuji, and the varieties people are loving on in this thread.