What are the basic types of chemical reactions?

There are 5 basic types of chemical reactions: 

1. Combination Reaction – In a combination reaction, two or more elements or compounds combine to form a single, more complex product. An example of a combination reaction is the combination of Iron and Sulfur to form iron sulfide. 
2. Decomposition Reaction – When a single complex compound breaks down into two or more simpler elements or compounds it is a decomposition reaction. It is the opposite of a combination reaction. An example of a decomposition reaction is the electrolysis of water into hydrogen and oxygen.
3. Single Replacement Reaction – In a single replacement reaction, one element replaces an element in another compound producing a new element and a new compound. An example of a single replacement reaction is the reaction of zinc and tin chloride, in which zinc replaces the tin in tin chloride to form zinc chloride and tin. This is also called a single displacement reaction. 
4. Double Replacement Reaction – In a double replacement reaction, the positive and negative ions of two different ionic compounds swap places to form two completely new compounds. The reaction between Potassium Chloride and Silver Nitrate is an example of a double replacement reaction. In this reaction potassium and silver switch places forming Potassium Nitrate and Silver Chloride. This is also called a double displacement reaction. 
5. Combustion Reaction – A combustion reaction is a type of redox reaction. In this type of reaction, a substance reacts with oxygen gas, releasing energy in the form of heat and light. Oxygen gas (O2) is an essential component in this type of reaction. An example of a combustion reaction is the reaction of hydrogen gas and oxygen gas, which produces water vapor.