A bi-folding door can open either inside or outside. They can all slide the same direction, or with larger doors such as a 7 panel, you can have some doors folding one way and the remainder to the opposite direction. You can even install them as a part of a corner arrangement.
Bi-folding doors can also be specified with one leaf serving as the main door, .so you can enter and exit without having to slide all the leaves back fully or partially every time.