Tubeless tyres don't contain an inner tube like regular tyres. Many cyclists (particularly those racing) prefer to run tubeless tyres as it saves weight, allows you to run lower pressures (which ride faster) and is more resistant to punctures, thanks to liquid sealant inside.
It is generally considered that 90-100psi is the ideal inflation as it allows the tyre to deform slightly over small bumps, rather than hitting them hard and losing speed as they bounce over. Regular tyres and tubes run a higher risk of flats at this level of inflation.
Not all rims and tyres are compatible with running a tubeless set-up though so you'll need to purchase a conversion kit containing replacement valves, sealant and rim tape to enjoy the advantages of life without tubes.