Tubeless tyres are pneumatic tires which do not have a separate tube inside.
Ordinary tires have a separate tube inside the tire. Tubeless tires are different in that they have continuous ribs. Integrally moulded, these ribs are sealed due to the pressure
Because tubeless tires do not need an inner tube, they are safer. The valve is mounted directly in the rim and and the wheel rim and tire form a perfect seal which is airtight. Tubeless tires are easier to fix if they get punctured as they have a special gel which reseals the tire if the tire is penetrated by a sharp object such as a nail. .