The difference is how each glass fibre is protected inside the cable. In a loose-tube cable the fibres lie freely inside a plastic tube, usually filled with gel, so the fibre is isolated from the pulling, bending and temperature movement of the cable around it. That construction suits outdoor duct, aerial and direct-buried routes, long lengths and high fibre counts. APAR's multi-tube loose-tube cables run from 6 to 1152 fibres for exactly those jobs.
In a tight-buffered cable each fibre carries its own thick plastic coating, so it can be handled, stripped and connectorised directly without a fan-out kit or gel cleaning. That makes it the usual choice for indoor patching, floor distribution and equipment connections, where lengths are short and the cable is terminated often. The breakout tight-buffer range covers 1 to 24 fibres for that work. The rule is simple: loose tube for the outside plant, tight buffer for the room.