What is the initial heating for?
It is used to start the reaction. They say it provides the activation energy (comparable to the energy which a child must provide to mount to a toboggan).
Then the reaction generates heat. How do you call such a reaction?
This is an exothermic reaction (the child slides on the toboggan!)
Two elementary substances combine to form a compound. What is the type of this reaction?
It's a synthesis reaction
Write the equation for the reaction!
$8Fe$ $ +$ $ S_8$ $\longrightarrow$ $ 8FeS$.