When magnesium metal is heated in air it begins to release large amounts of heat and light. what kind of a reaction is this an example of?

It is called exothermic reaction because it releases heat and light and it is called combustion reaction because it is reacting and is being oxidised by O2 to MgO. It can also be called as oxidation reaction since Mg is oxidised to MgO.

If we're talking about endothermic and exothermic reactions, then it is an exothermic reaction, since heat is being released.

Only one reactant yields 2 or more products. meaning you will only have 1 product and it will break down into 2 or more products. eg. h2o -> h2 + o2