Sometimes its hard to tell by the outside of an apple if it is ripe or not. The way to be sure is by the seeds; the seed on the left is ripe, and the one on the right still needs a week or two to be fully ripe.
However, some apples are best for baking right before they are fully ripe, and some folks prefer the tartness of a “green” (not quite ripe) apple. Other apples are only at their best when they are completely ripe.
Commercial apple varieties keep the best if they are picked before they are ripe, and you’ll sometimes find the seeds looking like the ones on the right. Unfortunately, none of these commercial varieties improve with age, and so you’ll never taste them at their optimum. Just another case for growing your own apples!