Start with the opening, not the photo
A single swing door needs clear floor for the arc. If the door would hit a toilet, a washer, or a person in a narrow hall, it is the wrong type even if you like the slab. A pocket door needs a hollow wall beside the opening and no pipes in that cavity. A barn door needs wall space to park and a header that can carry the weight. Bifolds and bypass doors belong on closets, not on a bedroom entry.
Measure the rough opening, the wall thickness, and the height of the doors already in the house. 80 inches matches most existing homes. 96 inches is for new work or rooms that are already tall. The number on the old slab is not the size to order.
Slab or prehung
A slab is the door only. Order it when the frame is square, the hinges land where the new door is bored, and you are keeping the jamb. A prehung door includes the frame and the hinges. Order that when the opening is new, the old frame is out of square, or you are changing the size. French interior doors and pocket doors are easier as a complete unit than as a slab you try to fit later.
Glass is a privacy decision. Clear or lightly textured glass borrows light for a kitchen, stair, or office. Frosted glass is for a bath or a bedroom that still wants daylight. Solid panels are for rooms that should stay quiet and closed.
Finish the set, then the hardware
Pick one finish for the project and order the doors together. White, black, and a light wood cover most modern houses. A black door is a contrast piece. A whole hall of mixed black, oak, and gloss white looks unsorted. Prefinished doors from one order match. The same color name bought later often does not.
Then match the hardware to the movement. Hinges and a lever for a swing door. A frame kit, an edge pull, and usually soft-close for a pocket door. A track, hangers, a floor guide, and a pull for a barn door. Concealed hinges belong on flush and frameless slabs. A sticking-out knob does not belong on a door that slides into a wall.