When you're planning a room, or doing a remodel, it is important to consider door size and swing. Doors come in a variety of sizes. Most of the standard residential doors in the US these days are 80 inches tall, but widths vary from 24 to 36 inches. in standard sizes.
One thing the handyman should consider is door swing. When you get to the store, you'll encounter the choice between left-hand and right-hand doors, so it is important to consider. The easiest way to explain door swing is to look at thus: Put your spine against the hinge side of the door. Whatever hand is convenient to the doorknob will decide whether the door is left-hand or right-hand.
Consider the photo of the lady.
Her spine is toward the hinges and the door knob is in her left hand. Thus, we have a left-hand door.
I'm glad I could clear that up for you.