In what kind of reaction is a compound formed from two reactants

The kind of reaction depends. if you have only one reactant ( element ) and another element make one element, hen it is called synthesis. If you have 2 compounds react , then it is called a double replacement reaction. if it is only one compound and one element, then it is called a single replacement reaction. if the reaction has say CH4 + 2 O2 ==> CO2 + H2O, then it is called a combustion reaction.

Where is the diagram? you need to be more specific in your question so we can you