Tubeless tyres and the straying nail
Tubeless tyres have been around since 1954. Today, they are the standard construction of tyres. In all likelihood, your’re already using them. Tubeless tyres have the mark “TL” or “Tubeless” on their sidewalls.

Construction of a tubeless tyre.
Needless to say, the tubeless tyre has no tubes. Instead, the tyre and the rim of your wheel form an air container. To seal in the air in this tyre-rim container, the inner wall of the tyre is thoroughly lined with an impermeable, airtight membrane.

How does the tubeless tyre make life better for you?
(1) It gives you more time between a puncture and a flat tyre.
In a tubed-type tyre, air is pumped into the tube. The resulting pressure causes the tube to press outwards against the inner wall of the tyre. It also causes the tube’s valve to fit into the one hole in the rim (the valve hole), thus sealing it. That’s how air is kept inside the tyre-rim container.

If a sharper object (eg. A nail) goes through the tread and punctures the tube, it causes the tube and its valve to immediately shrink back from the inner wall of the tyre. As a result, the valve hole in unsealed. Air escapes and the entire tyre collapses. To you, that means a flat tyre in a matter of seconds.

In a tubeless tyre, on the other hand, a nail puncturing the tyre does not expose any valve hole. Air escapes only through the actual space punctured by the nail. So, as long as the nail remains embedded in the tyre, it will take sometime before your tyre becomes completely flat. To you, that means more time to get to the workshop.

(2) Under normal conditions, it doesn’t get dislodged.
So long as your tubeless tyre is inflated to its proper pressure (at least above 10 psi), it cannot be dislodged. Except during an accident, of course, or if it hits an object (such as a kerb) obliquely and with substantial force.

Will inserting a tube in my tubeless tyre improve it?
No, because you cant insert a tube in a tubeless tyre without converting it completely into a tubed-type tyre and rim combination.