Chemical reactions can be classified into several types based on how reactants transform into products. The main types include synthesis, where two or more substances combine to form a new compound; decomposition, where a compound breaks down into simpler substances; and single replacement, where one element replaces another in a compound. Another category is double replacement, where parts of two compounds exchange places, and combustion, which involves a substance reacting with oxygen to produce energy, often in the form of heat and light. Understanding these types helps in predicting the outcomes of chemical reactions.