How does fire heat n burn things?What is the difference between the way fire n sun heats the its surroundings

Answer 1

Heat transfer is generally classify as being in three basic forms: conduction, radiation, and convection. Fire heats primarily by radiation from the visible and infrared light it emits and by convection and conduction from it's burning gases touching things directly. The space between the sun and earth is in vacuum, so the sun only heats the earth by radiation. Indirectly, though, once the sun heats things up (like air) those things can heat other things by radiation, convection, or conduction.

Answer 2

This might help, go down to the paragraph labeled combustion...
The sun is much more powerful than just straight fire. Nuclear fission and fusion occur in the sun, it doesn't just burn. It basically is a gigantic chemical reactor.