Give reason why the above reaction is known as a thermite reaction

I'm sorry, but you didn't provide a specific reaction. However, I can tell you that a thermite reaction generally refers to a redox reaction between a metal (often aluminium) and a metal oxide (often iron(III) oxide) which results in the metal oxide being reduced to the metal and the metal being oxidized. This reaction is highly exothermic, releasing a large amount of heat, hence the name "thermite" (from "thermal"). The reaction is:

Fe2O3 + 2Al → 2Fe + Al2O3 + heat

This reaction is used for welding in situations where it's not possible to use an electric weld, such as joining railway tracks.