‘Handing’ is the term used to describe the side of the door the hinges are on when the door is opening towards you (think of a refrigerator door). In Australia, if the hinges are on the left, it is a left handed door, and if they are on the right it is a right handed door. Australia's a confusing exception to the rule when it comes to 'handing' - in most other parts of the world it seems to be the other way around.
When in doubt it is best to prepare a simple sketch and take this with you when going to purchase your door.
Typical double door entry showing dimensions and clearance between the doors and frame.