What is the 'Father of All Bombs' that the West fears Russia can use against Ukraine?

Russia's thermobaric bomb, also called the 'Father of All Bombs', is said to be world's most powerful non-nuclear bomb, which the West reportedly fears Russia will use against Ukraine. The 44 metric tons of TNT equivalent works by using oxygen from surrounding air to generate high-temperature explosion. Analysts said that living things within the area of its detonation get vaporised.