Note
The Option (macOS) or Alt (Windows) key essentially allows you to create a new
direction line that is independent of the other for that anchor point. If you don’t hold
down the Option (macOS) or Alt (Windows) key, the direction handles would not be
split, so it would stay a smooth point.You can also Option-drag (macOS) or Alt-drag (Windows) the end of the direction handle
(called the direction point). An arrow is pointing to it in the first part of the figure. Either
method “splits” the direction handles so they can go in different directions.