Question: what are tubeless tyres bike?
Answer: As the name says, tubeless tyres dispense with the innertube. The tyre itself forms an airtight seal with the rim. A tubeless rim 'locks' the tyre beads in place; the fit between tyre and rim is tight by design. (As it's harder to remove the tyre, it's thus a bad idea to run a tyre with a tube on a tubeless rim.)