What is a vacuum bomb that Ukraine claims Russia is using?

A vacuum bomb, or thermobaric weapon, sucks in oxygen from the surrounding air to generate a high-temperature explosion, typically producing a blast wave of a significantly longer duration than that of a conventional explosive and is capable of vaporizing human bodies.

Also known as an aerosol bomb, it is a two-stage munition with the first charge distributing aerosols made up of very fine material from a carbon-based fuel to tiny metal particles. The second charge ignites that cloud creating a shock wave sucking up the oxygen and making a vacuum around its target. Experts have warned that the blast wave of a vacuum bomb lasts significantly longer than traditional explosives.