This is wirtten all in one paragraph, because that is what the question asks.
There are five main type of reactions under which you can classify most chemical reactions. Those are: combination (also known as shythesis), decomposition, combustion, single replacement and double replacement. You know that it is a synthesis (combination) reactions when there are two reactants and one single product (the two reactants are combined to form one single product). When you have one single reactant and two or more products, it is a decomposition reaction (the one reactant decomposed). When oxygen is one of the reactants the reaction is a combustion. When ions are exchanged you are in front of replacement reactions: if it is one ion which is exchanged it is single replacement, and if there are two reactants and two products in which the ions are exchanged, then it is a double replacement reaction.
