The pocket door slides into the wall, avoiding taking up floor space. Pocket doors are hung on a sliding door track.
Space-saving is the main advantage, they are unobstructive when open. This can help make the most use of small spaces. Frameless pocket doors are also an option. Self-closing & soft-closing mechanisms are available.
Kits are available with door, frame, track, handle and jambs. pocketdoorshop sells these.